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CCNP Route  EIGRP Overview
 

CCNP Route EIGRP Overview

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  • Fast convergence—EIGRP uses DUAL to achieve rapid convergence. A router running EIGRP stores its neighbors’ routing tables so that it can quickly adapt to changes in the network. If no appropriate route or backup route exists in the local routing table, EIGRP queries its neighbors to discover an alternative route. These queries are propagated until an alternative route is found, or it is determined that no alternative route exists.Partial updates—EIGRP sends partial triggered updates instead of periodic updates. These updates are sent only when the path or the metric for a route changes; they contain information about only that changed link rather than the entire routing table. Propagation of these partial updates is automatically bounded so that only those routers that require the information are updated. As a result, EIGRP consumes significantly less bandwidth than IGRP. This behavior is also different than link-state protocol operation, which sends a change update to all routers within an area. Multiple network layer support—EIGRP supports IP version 4 (IPv4), IP version 6 (IPv6), AppleTalk, and Novell NetWare Internetwork Packet Exchange (IPX) using protocol-dependent modules that are responsible for protocol requirements specific to the network layer. EIGRP’s rapid convergence and sophisticated metric offer superior performance and stability when implemented in IP, IPv6, IPX, and AppleTalk networks.Use of multicast and unicast—EIGRP uses multicast and unicast for communication between routers, rather than broadcast. As a result, end stations are unaffected by routing updates or queries. The multicast address used for EIGRP is 224.0.0.10.Other EIGRP features include the following:Variable-length subnet masking (VLSM) support—EIGRP is a classless routing protocol, which means that it advertises a subnet mask for each destination network; this enables EIGRP to support discontinuous subnetworks and VLSM. Seamless connectivity across all data link layer protocols and topologies—EIGRP does not require special configuration to work across any Layer 2 protocols. Other routing protocols, such as Open Shortest Path First (OSPF), require different configurations for different Layer 2 protocols, such as Ethernet and Frame Relay (as you will see in Chapter 3, “Implementing an OSPF-based Solution”). EIGRP was designed to operate effectively in both local-area network (LAN) and wide-area network (WAN) environments. In multiaccess topologies, such as Ethernet, neighbor relationships (also known as neighborships) are formed and maintained using reliable multicasting. EIGRP supports all WAN topologies: dedicated links, point-to-point links, and nonbroadcast multiaccess (NBMA) topologies. EIGRP accommodates differences in media types and speeds when neighbor adjacencies form across WAN links. The amount of bandwidth that EIGRP uses on WAN links can be limited.Sophisticated metric—EIGRP uses the same algorithm for metric calculation as IGRP, but represents values in a 32-bit format, rather than IGRP’s 24-bit format, to give additional granularity (thus, the EIGRP metric is the IGRP metric multiplied by 256). A significant advantage of EIGRP (and IGRP) over other protocols is its support for unequal metric load balancing that allows administrators to better distribute traffic flow in their networks.
  • Neighbor tableEIGRP routers use hello packets to discover neighbors. When a router discovers and forms an adjacency with a new neighbor, it includes the neighbor’s address and the interface through which it can be reached in an entry in the neighbor table. This table is comparable to the neighborship (adjacency) database used by link-state routing protocols (as described in Chapter 3). It serves the same purpose—ensuring bidirectional communication between each of the directly connected neighbors. EIGRP keeps a neighbor table for each network protocol supported; in other words, the following tables could exist: an IP neighbor table, an IPv6 neighbor table, an IPX neighbor table, and an AppleTalk neighbor table.Topology tableWhen the router dynamically discovers a new neighbor, it sends an update about the routes it knows to its new neighbor and receives the same from the new neighbor. These updates populate the topology table. The topology table contains all destinations advertised by neighboring routers; in other words, each router stores its neighbors’ routing tables in its EIGRP topology table. If a neighbor is advertising a destination, it must be using that route to forward packets; this rule must be strictly followed by all distance vector protocols. An EIGRP router maintains a topology table for each network protocol configured (IP, IPv6, IPX, and AppleTalk). Routing tableThe routing table holds the best routes to each destination and is used for forwarding packets; EIGRP successor routes are offered to the routing table. As discussed in Chapter 1, “Routing Services,” if a router learns more than one route to exactly the same destination from different routing sources, it uses the administrative distance to determine which route to keep in the routing table. By default, up to 4 routes to the same destination with the same metric can be added to the routing table (recall that the router can be configured to accept up to 16 per destination). The router maintains one routing table for each network protocol configured.
  • Reliable Transport Protocol (RTP)RTP is responsible for guaranteed, ordered delivery of EIGRP packets to all neighbors. RTP supports intermixed transmission of multicast or unicast packets. For efficiency, only certain EIGRP packets are transmitted reliably. For example, on a multiaccess network that has multicast capabilities, such as Ethernet, it is not necessary to send hello packets reliably to all neighbors individually, so EIGRP sends a single multicast hello packet containing an indicator that informs the receivers that the packet need not be acknowledged. Other types of packets, such as updates, indicate in the packet that acknowledgment is required. RTP contains a provision for sending multicast packets quickly even when unacknowledged packets are pending, which helps ensure that convergence time remains low in the presence of varying speed links. Neighbor discovery/recovery mechanismEIGRP's neighbor discovery mechanism enables routers to dynamically learn about other routers on their directly attached networks. Routers also must discover when their neighbors become unreachable or inoperative. This process is achieved with low overhead by periodically sending small hello packets. As long as a router receives hello packets from a neighboring router, it assumes that the neighbor is functioning, and the two can exchange routing information. Reliable Transport Protocol (RTP)RTP is responsible for guaranteed, ordered delivery of EIGRP packets to all neighbors. RTP supports intermixed transmission of multicast or unicast packets. For efficiency, only certain EIGRP packets are transmitted reliably. For example, on a multiaccess network that has multicast capabilities, such as Ethernet, it is not necessary to send hello packets reliably to all neighbors individually, so EIGRP sends a single multicast hello packet containing an indicator that informs the receivers that the packet need not be acknowledged. Other types of packets, such as updates, indicate in the packet that acknowledgment is required. RTP contains a provision for sending multicast packets quickly even when unacknowledged packets are pending, which helps ensure that convergence time remains low in the presence of varying speed links. DUAL finite-state machineDUAL embodies the decision process for all route computations. DUAL tracks all routes advertised by all neighbors and uses distance information, known as the composite metric or cost, to select efficient, loop-free paths to all destinations. Protocol-dependent modulesEIGRP’s protocol-dependent modules are responsible for network layer protocol-specific requirements. EIGRP supports IP, IPv6, AppleTalk, and IPX; each protocol has its own EIGRP module and operates independently from any of the others that might be running. The IP-EIGRP module, for example, is responsible for sending and receiving EIGRP packets that are encapsulated in IP. Likewise, IP-EIGRP is also responsible for parsing EIGRP packets and informing DUAL of the new information that has been received. IP-EIGRP asks DUAL to make routing decisions, the results of which are stored in the IP routing table. IP-EIGRP is also responsible for redistributing routes learned by other IP routing protocols.
  • When a router discovers a new neighbor, an update is sent to and received from its new neighbor populating the topology table (containing destinations advertised by all neighbors)The topology table:Updated when a directly connected route or interface changes or when a neighboring router reports a change to a routeEntry for a destination exists in either active or passive state:Passive state: router is not performing a recomputationActive state: router is performing a recomputationRecomputation occurs when the destination has no feasible successors (initiated by sending a query packet to each of the neighboring routers
  • How EIGRP uses these tables:EIGRP uses the Neighbor table to list adjacent routers.Topology table lists all learned routes to each destinationRouting table contains the best route (successor route) and backup route (feasible successor route)When a neighbor adjacency is formed, it records the neighbor’s address and the interface through which it can be reached as an entry in the neighbor table. One neighbor table exists for each protocol-dependent module.The EIGRP neighbor table is comparable to the adjacencies database that link-state routing protocols use and serves the same purpose: to ensure bidirectional communication between each of the directly connected neighbors.When the hello packet is sent, it advertises a hold time (time a router reports a neighbor as reachable and operational). If a hello packet from a neighboring router is not received within the hold time, it expires, and DUAL is informed of the topology change.The neighbor-table includes information required by RTP.Sequence numbers are used to match acknowledgments with data packets (helping to check out-of-order packets).transmission list is used to queue packets for possible retransmission on a per-neighbor basis. Round-trip timers are kept in the neighbor-table entry to estimate an optimal retransmission interval.
  • The command output also lists the networks known by this router through the EIGRP routing process. The codes used in the first column of this output indicate the state of the entry. Passive and Active refer to the EIGRP state with respect to this destination. Update, Query, and Reply refer to the type of packet being sent. The codes are as follows:Passive (P)—This network is available, and installation can occur in the routing table. Passive is the correct state for a stable network, indicating that no EIGRP computations are being performed for this route.Active (A)—This network is currently unavailable, and installation cannot occur in the routing table. Being active means that outstanding queries exist for this network, indicating that EIGRP computations are being performed for this route.Update (U)—This network is being updated (indicating that an update packet is being sent). This code also applies if the router is waiting for an acknowledgment for this update packet.Query (Q)—There is an outstanding query packet for this network, indicating that a query packet was sent. This code also applies if the router is waiting for an acknowledgment for a query packet.Reply (R)—The router is generating a reply for this network, indicating that a reply packet was sent, or is waiting for an acknowledgment for the reply packet.Stuck-in-active (S)—There is an EIGRP convergence problem for this network.
  • Notice that the routing table includes routes, to null0, for the advertised (summarized) routes. Cisco IOS Software automatically puts these routes in the table; they are called summary routes. Null 0 is a directly connected, software-only interface. The use of the null0 interface prevents the router from trying to forward traffic to other routers in search of a more precise, longer match. For example, if the R1 router in Figure 2-20 receives a packet to an unknown subnet that is part of the summarized range—172.16.3.5 for example—the packet matches the summary route based on the longest match. The packet is forwarded to the null0 interface (in other words, it is dropped, or sent to the bit bucket), which prevents the router from forwarding the packet to a default route and possibly creating a routing loop.
  • The following example examines partial entries for network 10.1.1.0/24 in the topology tables for Routers C, D, and E, to give you a better understanding of EIGRP behavior. The partial topology tables indicate the following:AD—The advertised distance is equal to the cost of the path to network 10.1.1.0/24 as advertised by neighboring routers. For example, consider Router E's neighbors: Router D has an AD of 2 and Router C has an AD of 3, for 10.1.1.0/24.FD—The feasible distance is equal to the sum of the AD for a neighbor to reach 10.1.1.0/24, plus the metric to reach that neighbor. For example, again consider Router E: The FD of the route to 10.1.1.0/24 via Router D is Router D's AD (2) plus the metric to reach Router D from Router E (1), for a total of 3. The FD of the route to 10.1.1.0/24 via Router C is Router C's AD (3) plus the metric to reach Router C from Router E (1), for a total of 4.Successor—The successor is the forwarding path used to reach network 10.1.1.0/24. The cost of this path is equal to the FD. For example, Router E chooses the path to 10.1.1.0/24 with the lowest FD, which is via Router D. This is the route that Router E puts in its routing table.FS—The feasible successor is an alternative loop-free path to reach network 10.1.1.0/24. For example, in Router C, the path via Router D is an FS because the AD (2) is less than the FD (3) via the successor Router B. Routers D and E do not have any FSs because the AD of the alternate routes are not less than the FD of their current successors.
  • Routers B and D detect a link failure. After being notified of the link failure, DUAL does the following:At Router D, it marks the path to network 10.1.1.0/24 through Router B as unusable.
  • The following steps then occur:At Router D, there is no FS to network 10.1.1.0/24, because the AD via Router C (3) is greater than the FD via Router B (2). Therefore, DUAL does the following:Sets the metric to network 10.1.1.0/24 as unreachable (–1 is unreachable).Because an FS cannot be found in the topology table, the route changes from the passive state to the active state. In the active state, the router sends out queries to neighboring routers looking for a new successor.Sends a query to Routers C and E for an alternative path to network 10.1.1.0/24.Marks Routers C and E as having a query pending (Q).At Router E, DUAL marks the path to network 10.1.1.0/24 through Router D as unusable.At Router C, DUAL marks the path to network 10.1.1.0/24 through Router D as unusable.
  • The following steps then occur:At Router D:DUAL receives a reply from Router C that indicates no change to the path to network 10.1.1.0/24.DUAL removes the query flag from Router C.DUAL stays active on network 10.1.1.0/24, awaiting a reply from Router E to its query (Q).At Router E, there is no FS to network 10.1.1.0/24, because the AD from Router C (3) is not less than the original FD (also 3).DUAL generates a query to Router C.DUAL marks Router C as query pending (Q).At Router C, DUAL marks the path to network 10.1.1.0/24 through Router E as unusable.
  • The following steps then occur:At Router D:DUAL stays active on network 10.1.1.0/24, awaiting a reply from Router E (q).At Router E:DUAL receives a reply from Router C indicating no change.It removes the query flag from Router C.It calculates a new FD and installs a new successor route in the topology table.It changes the route to network 10.1.1.0/24 from active to passive (converged).
  • The following steps then occur:At Router DDUAL receives a reply from Router E.It removes the query flag from Router E.It calculates a new FD.It installs new successor routes in the topology table. Two routes (through Routers C and E) have the same FD, and both are marked as successors.It changes the route to network 10.1.1.0/24 from active to passive (converged).At Router D, two successor routes are in the topology table for network 10.1.1.0/24. Both successor routes are listed in the routing table, and equal-cost load balancing is in effect.The network is stable and converged.
  • At Router D, two successor routes are in the topology table for network 10.1.1.0/24. Both successor routes are listed in the routing table, and equal-cost load balancing is in effect.The network is stable and converged.
  • IP addressing plan: The IP addressing plangoverns how EIGRP can be deployed and how well the EIGRP deployment will scale. A detailed IP subnet and addressing plan must be produced, and should be hierarchical to enable EIGRP summarization, allow the network to scale more easily, and to optimize EIGRP behavior.Network topology: The topology consists of the devices (routers, switches, and so on) and the links connecting them. A detailed network topology should be created to assess EIGRP scalability requirements and to determine which EIGRP features might be required (for example, EIGRP stub routing).EIGRP traffic engineering: By changing the interface metrics, EIGRP traffic engineering can be deployed to improve bandwidth utilization and enable the administrator to have control over traffic patterns.
  • Interfaces are configured on routers R1 and R2.
  • Specificnetwork subnets are identified (without a wildcard mask) on R1 and R2. The EIGRP adjacency automatically establishes once the R2 S0/0/0 network is configured.
  • Notice that the R1 running configuration did not recognize the specific configured subnets but instead configured the classful networks.As well, the R1 routing table only included the classful 172.17.0.0/16 network and not the more specific 172.17.2.0/24.
  • Notice that the R2 running configuration did not recognize the specific configured subnets but instead configured the classful networks.As well, the R2 routing table only included the classful 172.16.0.0/16 network and not the more specific 172.16.1.0/24.However, pings to the R1 LAN would still be successful.
  • One problem that arises from this automatic summarization configuration is that R2 not also advertises EIGRP messages out of its S0/0/0 interface, it also advertises out of its S0/0/1 interface to the non-EIGRP neighbor.This is because R2 recognized the classful 192.168.1.0/24 and interface S0/0/1 is also on this classful network.To rectify this situation, the networks should be configured to include the wildcard mask.Without the wildcard mask, R2 would still send EIGRP packets to the external network out of interface S0/0/1, which would waste bandwidth and CPU cycles and would provide unnecessary information to the external network.
  • In this case, the router can be configured with a wildcard mask so the router does not try to form an adjacency with the router in the other AS. For example, on R2 the EIGRP 100 configuration is first erased and then reentered but now includes the wildcard mask.
  • This makes EIGRP send messages out of interfaces Fa0/0 and S0/0/1 only.Also notice that the mask is now included in the Routing for Networks section.
  • In this configuration, routing updates are no longer sent on interface Fa0/0 of R1 and R2.The alternative configuration makes all interfaces passive and then makes interface S0/0/0 not passive. This method is efficient when there are many interface that should be passive and only a few that should not be passive.Commands to verify include;show ip protocolsshow ip eigrp neighbors
  • Verify the routing tables of the routers.
  • The network must be reachable therefore, a static route to the desireddestination network is configured and connectivity to it verified.The ip default-network command is then used to specify the network as the default gateway. This install the gateway of last resort in the routing table of R2 but does not install it into the routing table of R1.The static is then redistributed into EIGRP and automatically gets propagated to the R1 router.
  • The routing table of R2 now has the gateway of last resort set and a static route identified as a candidate default route (*).R1 also has the gateway of last resort set and an EIGRP entry as a candidate default route that was learned from an external source (it was redistributed into EIGRP on R2) with an administrative distance of 170.
  • Specify the outgoing interface creates.Enter the network 0.0.0.0 command and the gateway of last resort is propagated to the EIGRP AS.
  • An alternative is to specify the outgoing interface creates.Enter the network 0.0.0.0 command.Redistribute the static route.The gateway of last resort is propagated to the EIGRP AS.
  • Routers R1 and R2 have both been configured for EIGRP and are advertising their LAN and serial networks accordingly. Notice that is connected to the 10.10.10.0 /24 network while R2 is connected to 10.20.20.0 /24 and that those networks are separated by a network that is not in the 10.0.0.0/8 network.Although Router R1 is configured to advertise the 10.10.10.0 /24 network, automatic summarization is configured (by default), and therefore it summarizes the 10.10.10/24 network to the classful 10.0.0./8 network when sending an update to R2.
  • R2 ignores the 10.0.0.0/8 update from R1 because it is already connected to a 10.0.0.0/8 network.
  • For example, if the R2 router receives a packet destined to the 10.0.0.0/8 network other than the directly connected 10.20.20.0/24, then the packet is forwarded to the null0 interface (in other words, it is dropped, or sent to the bit bucket), which prevents the router from forwarding the packet to a default route and possibly creating a routing loop.
  • Automatic summarization is disabled on R1 using the no auto-summary router configuration command.A DUAL neighbor change message appears occurs and R1 is no longer summarizing the 10.10.10/24 networkto the 10.0.0.0/8 network.
  • The R2 routing table now includes the R1 LAN.
  • Routers R1 and R2 are no longer auto summarizing at the major network boundary and all the subnet routes are carried into R3s routing table. R3 will not auto summarize the 10.10.10.0 and 10.10.20.0 subnets because it does not own the 10.0.0.0 network and would therefore send routing information about those subnets to the WAN.To correct this situation, configure the ip summary-address eigrp command.The resulting configuration would make R3 advertise only one route (10.10. 0.0/16) to the WAN.
  • The deployment choice inevitably depends on WAN resources available at the location.
  • Router R1 is a hub for the two spoke routers, R2 and R3.Split horizon is disabled by default on Frame Relay physical interfaces. Therefore routes from Router R2 can be sent to Router R3, and vise-versa. Only the encapsulation frame-relay command is required since Inverse-ARP will detect most FR settings.Note that inverse ARP does not provide dynamic mapping for the communication between routers R2 to R3 because they are not connected with a PVC; this must be configured manually.
  • Split horizon is disabled by default on Frame Relay physical interfaces. Therefore routes from Router R2 can be sent to Router R3, and vise-versa. Note that inverse ARP does not provide dynamic mapping for the communication between routers R2 to R3 because they are not connected with a PVC; this must be configured manually.
  • Note:  Router R1's configuration includes a frame-relay map to its own IP address on the Frame Relay interface so that the Serial 0/0 local IP address can be pinged from Router R1 itself.
  • Multipoint subinterfaces are logical interfaces emulating a multi-access network and act like an NBMA physical interface.Partial mesh Frame Relay networks must deal with split horizon issues, which prevent routing updates from being retransmitted on the same interface on which they were received.
  • A multipoint subinterface Serial 0/0/0.1 is created and an IP address is assigned to it. Split horizon is enabled by default on Frame Relay multipoint interfaces. In this example, routers R2 and R3 need to provide connectivity between their connected networks, so EIGRP split horizon is disabled on the multipoint subinterface of router R1 with the no ip split-horizon eigrp as-number command. Manual IP address-to-DLCI mapping is also configured, using the frame-relay map commands with the broadcast keyword.The EIGRP configuration is not changed from the basic deployment. EIGRP is enabled using AS number 100 and the proper interfaces and networks are included in EIGRP using the network commands under the EIGRP routing process.
  • Router R1 is configured with a neighbor command for Router R2 and will therefore not accept multicast packets on Serial 0/0/0.1 anymore. In order to establish an adjacency with Router R1, Router R2 must also be configured with a neighbor command, for Router R1
  • The neighbor command enables Router R2 to use unicast packets, which will be accepted by Router R1. In this scenario, Router R3 is not configured with a neighbor command for Router R1, nor is Router R1 configured with a neighbor command for Router R3. Therefore, routers R1 and R3 will not form an adjacency.
  • Logical interfaces emulating a leased line network and provide a routing equivalent to point-to-point physical interfaces. EIGRP neighbor loss detection is quite fast on point-to-point subinterfaces because the default values of the EIGRP hello timer and the EIGRP hold timer are identical to the values used on point-to-point physical links (5 seconds for the hello timer and 15 seconds for the hold timer). In the worst case, the neighbor loss is detected within 15 seconds. Another reason that neighbor loss is fast is that a Frame Relay subinterface is declared down if the DLCI attached to the interface is lost; neighbor loss detection is immediate. For multipoint subinterfaces, all of the PVCs attached to it must be lost for the interface to be declared down.
  • On Router R1, two point-to-point subinterfaces, Serial 0/0.2 and Serial 0/0.3, are created and IP addresses are assigned to them. The IP address-to-DLCI mapping is provided for each subinterface. The EIGRP configuration is not changed from the basic deployment.
  • Router R1 forms the adjacency with Router R2 over its serial0/0/0.2 point-to-point interface and with Router R3 over its serial0/0/0.3 point-to-point subinterface. Likewise, Routers R2 and R3 form the adjacency with Router R1 over the serial 0/0/0.1 point-to-point subinterface. Router R3 has one neighbor, Router R1, over its serial0/0.1 point-to-point subinterface.
  • Routers R1 and R2 are configured for EIGRP as if there were a corporate core network between them. The customer has to agree upon the EIGRP parameters (such as the AS number, authentication password, and so on) with the service provider to ensure connectivity; these parameters are often governed by the service provider.The PE routers receive routing updates from the CE routers and install these updates in the appropriate VRF table. This part of the configuration and operation is the SP's responsibility.
  • Observe the resulting EIGRP neighbor tables on the R1 and R2 routers. Notice that Router R1 establishes an EIGRP neighbor relationship with the PE1 router, and Router R2 establishes an EIGRP neighbor relationship with the PE2 router. Routers R1 and R2 do not establish an EIGRP neighbor relationship with each other.
  • EIGRP needs to be enabled with the correct AS number (the same on both routers R1 and R2). The network commands must include all of the interfaces that will run EIGRP, including the link toward the PE routers (routers PE1 and PE2) over which the routers R1 and R2 will form their neighbor relationship. From the EIGRP perspective, the MPLS backbone and routers PE1 and PE2 are not visible. A neighbor relationship is established directly between routers R1 and R2 over the MPLS backbone
  • The resulting EIGRP neighbor tables on the R1 and R2 routers. Notice that Router R1 establishes an EIGRP neighbor relationship with the PE1 router, and Router R2 establishes an EIGRP neighbor relationship with the PE2 router. Routers R1 and R2 do not establish an EIGRP neighbor relationship with each other.
  • Router R1 is configured to support up to three equal-cost paths. Router R1 will keep the routes via R2, R3, and R4 in its routing table because the three paths have the same metric (cost) of 40 (as shown in the FD column). The path through router R5 is not used because the metric is bigger than 40 (it is 60). Even if this metric was the same as the others, only three of the four routes would be used because of the maximum-paths 3 command.
  • Router R1 uses Router R3 as the successor because its FD is lowest (20).The variance 2 command makes the path through Router R2 meet the criteria for load balancing becausethe FD through Router R2 (30) is less than twice the FD through the successor Router R3 (2*20 = 40). Router R4 is not considered because it was not a feasible successor and only feasible successors are considered. Also the FD through Router R4 (45) is greater than twice the FD for the successor (Router R3) (2*20 = 40). Router R5 is not considered for load balancing even though it is a feasible successor because the FD through router R5 (50) is more than twice of the FD for the successor through router R3 (2*20 = 40). The load is balanced proportional to the bandwidth. The FD of the route via router R2 is 30, and the FD of the route via router R3 is 20; the ratio of traffic between the two paths (via R2 : via R3) is therefore 3/5 : 2/5.
  • The Cisco IOS assumes that point-to-point Frame Relay subinterfaces are operating at the default speed of the interface. In many implementations only fractional speeds (such as a fractional T1) are available thereforethe bandwidth should be configured to match the contracted CIR.
  • When configuring multipoint interfaces (especially for Frame Relay, but also for ATM and ISDN PRI), remember that the bandwidth is shared equally by all neighbors. That is, EIGRP uses the bandwidth command on the physical interface divided by the number of Frame Relay neighbors connected on that physical interface to get the bandwidth attributed to each neighbor. EIGRP configuration should reflect the correct percentage of the actual available bandwidth on the line.The configuration of the bandwidth command in an NBMA cloud depends on the design of the VCs. If the serial line has many VCs in a multipoint configuration, and all of the VCs share bandwidth evenly, set the bandwidth to the sum of all of the CIRs. For example, each VC's CIR is set to 56 Kbps.Since there are 4 VCs, the bandwidth is set to 224 (4 x 56).
  • One circuit has been provisioned for a 56-kbps CIR, and the other three circuits have a higher CIR of 256 kbps. The interface on R1 has been configured for a bandwidth equal to the lowest CIR multiplied by the number of circuits being supported (56 * 4 = 224), as shown in the example. This configuration protects against overwhelming the slowest-speed circuit in the topology.
  • The link to R5 is the low-speed circuit so it is configured as point-to-point. The remaining circuits are designated as multipoint, and their respective CIRs are added up to set the interface’s bandwidth (256 + 256 + 256 = 768). On the multipoint interface, the bandwidth is shared equally among all circuits therefore the bandwidth will be split into 3, with 256 kbps allocated to each circuit.
  • MD5 authentication is configured on the serial 0/0/1 interface with the ip authentication mode eigrp 100 md5 command. When MD5 authentication is configured, an MD5 keyed digest is added to each EIGRP packet sent and is checked in each received EIGRP packet.The key chain R1chain command enters configuration mode for the R1chain key chain. Two keys are defined in this key chain. Each key has an authentication string and lifetime specified. The network administrator wants to change the keys on all the routers in the network each month to improve the security. The administrator configures an overlap of one week to change the keys on all the routers; the validity of key 2 is configured 1 week before the expiration of key 1 to allow the new key to be applied to all the routers in the network.Key 1 is set to FIRST-KEY with the key-string FIRST-KEY command. This key is acceptable for use on packets received by R1 from January 1, 2009 onward, as specified in the accept-lifetime 04:00:00 Jan 1 2009 infinite command. However, the send-lifetime 04:00:00 Jan 1 2009 04:00:00 Jan 31 2009 command specifies that this key was only valid for use when sending packets until January 31, 2009; it is no longer valid for use in sending packets after January 31st 2009.Key 2 is set to SECOND-KEYwith the key-string SECOND-KEY command. This key is acceptable for use on packets received by R1 from January 25, 2009 onward, as specified in the accept-lifetime 04:00:00 Jan 25 2009 infinite command. This key can also be used when sending packets from January 25, 2009 onward, as specified in the send-lifetime 04:00:00 Jan 25 2009 infinite command.The ip authentication key-chain eigrp 100 R1chain command configured on the Serial 0/0/1 interface specifies that the EIGRP key chain R1chain is to be used on this interface.Recall that the router uses the first, by key number, valid key for sending packets. As a result of this configuration, router R1 will use key 1 for sending, from January 1st to 31st, 2009, and will used key 2 for sending as of 4:00 am on January 31st 2009. Router R1 will accept key 1 for received packets, from January 1st 2009, and will also accept key 2 for received packets, from January 25th 2009. All other MD5 packets will be dropped.MD5 authentication is configured on the serial 0/0/1 interface with the ip authentication mode eigrp 100 md5 command. When MD5 authentication is configured, an MD5 keyed digest is added to each EIGRP packet sent and is checked in each received EIGRP packet.The key chain R1chain command enters configuration mode for the R1chain key chain. Two keys are defined in this key chain. Each key has an authentication string and lifetime specified. The network administrator wants to change the keys on all the routers in the network each month to improve the security. The administrator configures an overlap of one week to change the keys on all the routers; the validity of key 2 is configured 1 week before the expiration of key 1 to allow the new key to be applied to all the routers in the network.Key 1 is set to FIRST-KEY with the key-string FIRST-KEY command. This key is acceptable for use on packets received by R1 from January 1, 2009 onward, as specified in the accept-lifetime 04:00:00 Jan 1 2009 infinite command. However, the send-lifetime 04:00:00 Jan 1 2009 04:00:00 Jan 31 2009 command specifies that this key was only valid for use when sending packets until January 31, 2009; it is no longer valid for use in sending packets after January 31st 2009.Key 2 is set to SECOND-KEYwith the key-string SECOND-KEY command. This key is acceptable for use on packets received by R1 from January 25, 2009 onward, as specified in the accept-lifetime 04:00:00 Jan 25 2009 infinite command. This key can also be used when sending packets from January 25, 2009 onward, as specified in the send-lifetime 04:00:00 Jan 25 2009 infinite command.The ip authentication key-chain eigrp 100 R1chain command configured on the Serial 0/0/1 interface specifies that the EIGRP key chain R1chain is to be used on this interface.Recall that the router uses the first, by key number, valid key for sending packets. As a result of this configuration, router R1 will use key 1 for sending, from January 1st to 31st, 2009, and will used key 2 for sending as of 4:00 am on January 31st 2009. Router R1 will accept key 1 for received packets, from January 1st 2009, and will also accept key 2 for received packets, from January 25th 2009. All other MD5 packets will be dropped.
  • The key chain R2chain command enters configuration mode for the R2chain key chain. Two keys are defined. Key 1 is set to FIRST-KEY with the key-string FIRST-KEY command. This key is acceptable for use on packets received by R2 from January 1, 2009 onward, as specified in the accept-lifetime 04:00:00 Jan 1 2009 infinite command. This key can also be used when sending packets from January 1, 2009 onward, as specified in the send-lifetime 04:00:00 Jan 1 2009 infinite command.Key 2 is set to SECOND-KEYwith the key-string SECOND-KEY command. This key is acceptable for use on packets received by R2 from January 25, 2009 onward, as specified in the accept-lifetime 04:00:00 Jan 25 2009 infinite command. This key can also be used when sending packets from January 25, 2009 onward, as specified in the send-lifetime 04:00:00 Jan 25 2009 infinite command.As a result of this configuration, router R2 will use key 1 for sending, from January 1st 2009, because it is the first valid key in the key chain. (Of course, if key 1 is deleted in the future, key 2 would be used for sending.) Router R2 will accept key 1 for received packets, from January 1st 2009, and will also accept key 2 for received packets, from January 25th 2009. All other MD5 packets will be dropped.
  • MD5 authentication on both R1 and R2, but R1 key 2 (that it uses when sending) changed.The output of the debug eigrp packets command on R2 shown in the figure illustrates that R2 is receiving EIGRP packets with MD5 authentication, with a key-id equal to 2, from R1, but that there is an authentication mismatch. The EIGRP packets from R1 are ignored, and the neighbor relationship is declared to be down. The output of the show ip eigrp neighbors command confirms that R2 does not have any EIGRP neighbors.The two routers keep trying to re-establish their neighbor relationship. Because of the different keys used by each router in this scenario, R1 will authenticate hello messages sent by R2 using key 1. However, when R1 sends a hello message back to R2 using key 2, there will be an authentication mismatch. From R1’s perspective, the relationship appears to be up for awhile, but then it times out, as illustrated by the following messages received on R1. The output of the show ip eigrp neighbors command on R1 also illustrates that R1 does have R2 in its neighbor table for a short time.
  • The following presents a network example where a single lost route might result in an enormous amount of queries sent throughout the EIGRP domain. The route to the network 10.1.1.0 on router R1 is lost and router R1 sends a query to all neighboring routers on all interfaces except the interface of the successor (because of split horizon). In this case the query is sent to router R2 and then R2 cascades the query to its neighbors, because it has no information about the lost route, and so on. Each query requires a reply from the neighbor; the amount of EIGRP traffic increases. In this network topology there is no redundant path to network 10.1.1.0 available, and the EIGRP query propagation process is far from being efficient. Many queries are sent and each query is followed by a reply. Several solutions exist to optimize the query propagation process and to limit the amount of unnecessary EIGRP load on the links, including summarization, redistribution, and using EIGRP stub routing feature.

CCNP Route  EIGRP Overview CCNP Route EIGRP Overview Presentation Transcript

  • © 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicROUTE v6 Chapter 21Chapter 2:Configuring the EnhancedInterior Gateway RoutingProtocolCCNP ROUTE: Implementing IP Routing
  • Chapter 22© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicChapter 2 Objectives Describe the basic operation of EIGRP. Plan and implement EIGRP routing. Configure and verify EIGRP routing. Configure and verify basic EIGRP in an enterprise WAN. Configure and verify EIGRP Authentication. Describe and configure EIGRP optimization mechanisms;verify and troubleshoot the overall implementation.
  • Chapter 23© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicUnderstandingEIGRPTerminologyand Operation
  • Chapter 24© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Capabilities and Attributes EIGRP is a Cisco-proprietary distance-vector protocol withlink-state features. EIGRP features include:• Fast convergence• Partial updates• Multiple network layer support• Use of multicast and unicast communication• Variable-length subnet masking (VLSM) support• Seamless connectivity across all data link layer protocols andtopologies• By default, it performs automatic route summarization at majornetwork boundaries (can be disabled) but can also be configured tosummarize on interfaces.
  • Chapter 25© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Terminology Neighbor table Topology table Routing table Advertised Distance (AD) Feasible Distance (FD) Successor Feasible successor (FS) Passive Versus Active Routes
  • Chapter 26© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Tables Neighbor table• Contains EIGRP neighbor addresses and the interface through whichthey can be reached. Topology table• Contains all destinations advertised by neighboring routers. Routing table• Contains EIGRP successor routes.
  • Chapter 27© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicAD versus FD Advertised Distance (AD)• Advertised distance (AD), also referred to as the ReportedDistance, is the cost between the next-hop router and the destination. Feasible Distance (FD)• Feasible distance (FD) is the cost between the local router and thenext-hop router plus the next-hop router’s AD to the destinationnetwork.
  • Chapter 28© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicSuccessor and Feasible Successor Successor• A successor is a neighboring router that has a least-cost path to adestination (the lowest FD) that is guaranteed not to be part of a routingloop.• Successor routes are offered to the routing table to be used forforwarding packets.• Multiple successors can exist if they have the same FD. Feasible successor (FS)• A feasible successor is a neighbor that is closer to the destination, but itis not the least-cost path.• A feasible successor ensures a loop-free topology because it must havean AD less than the FD of the current successor route.• Feasible successors are selected at the same time as successors but arekept in the topology table as backups to the successor routes.• The topology table can maintain multiple feasible successors for adestination.
  • Chapter 29© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicPassive versus Active Routes Passive Route• A route is considered passive when the router is not performingrecomputation on that route.• Passive is the operational, stable state. Active route• A route is active when it is undergoing recomputation.
  • Chapter 210© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicKey EIGRP Technologies Reliable Transport Protocol (RTP)• Responsible for guaranteed, ordered delivery of EIGRP packets to allneighbors. Neighbor discovery/recovery mechanism• Enables EIGRP routers to dynamically learn when their neighborsbecome unreachable or inoperative by periodically sending small hellopackets. Protocol-dependent modules (PDMs)• Responsible for network layer protocol-specific requirements such asIP, IPv6, AppleTalk, and Novell NetWare. DUAL finite-state machine• Diffusing Update Algorithm (DUAL) is the routing algorithm that tracksall routes advertised by all neighbors and uses distanceinformation, known as the composite metric, to select efficient, loop-freepaths to all destinations.
  • Chapter 211© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicReliable Transport Protocol EIGRP cannot use the services of UDP or TCP since IPXand Appletalk do not use the TCP/IP protocol suite. Reliable Transport Protocol (RTP) is the Transport layerprotocol uniquely used by EIGRP for the delivery andreception of EIGRP packets.• RTP is similar to TCP but is a Cisco proprietary. RTP provides reliable or unreliable service as the situationwarrants.• Reliable packets (Update, Query, Reply) require explicitacknowledgement while unreliable packets (Hello, ACK) do not.
  • Chapter 212© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicNeighbor Discovery / Recovery EIGRP routers actively establish relationships with theirneighbors. Adjacencies are established using small Hello packetswhich are sent every 5 or 60 seconds.• If a neighbor misses 3 consecutive Hello packets then the route isconsidered invalid.• Default = 15 seconds or 180 seconds.
  • Chapter 213© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicNeighbor Discovery / Recovery
  • Chapter 214© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicProtocol-Dependent Modules Various routed protocols are supported through its PDMs.• Provides independence from routed protocols.• PDMs are modular, scalable and adaptable.• EIGRP can adapt to new or revised routed protocols.• PDMs protect EIGRP from painstaking revision. Each PDM is responsible for all functions related to itsspecific routed protocol.
  • Chapter 215© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicProtocol-Dependent ModulesEIGRP maintainsindividual tables foreach routed protocol.
  • Chapter 216© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicDUAL finite-state machine DUAL uses the Neighbor and Topology tables to calculateroute information. When a link fails, DUAL looks for a feasible successor in itsNeighbor and Topology tables.• It compares all routes advertised by neighbors by using a compositemetric for each route.• Lowest-cost paths are then inserted into the routing table.
  • Chapter 217© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP PacketFrame HeaderFrame PayloadCRCIPHeaderProtocol Number(EIGRP = 88)EIGRPHeaderEIGRPMessageOn a LAN, the EIGRPpacket is encapsulatedin an Ethernet framewith a destinationmulticast MAC address:01-00-5E-00-00-0AThe destination IP address isset to the multicast 224.0.0.10and the EIGRP protocol fieldis 88.The EIGRPheader identifiesthe type of EIGRPpacket andautonomoussystem number.The EIGRPmessageconsists ofthe Type /Length /Value (TLV).
  • Chapter 218© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Header EIGRP uses these 5 packet types to maintain its varioustables and establish complex relationships with neighborrouters:• Hello• Acknowledgment• Update• Query• Reply
  • Chapter 219© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Header
  • Chapter 220© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Packet
  • Chapter 221© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicHello Packets EIGRP relies on Hello packets to discover, verify, andrediscover neighbor routers. EIGRP Hello packets are multicast to 224.0.0.10. Hello packets are always sent unreliably and therefore donot require acknowledgment.
  • Chapter 222© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Hello Packets
  • Chapter 223© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicHello Packets Hellos are sent at a fixed (and configurable) interval, calledthe Hello interval.• Hello/Hold timers do not need to match.• To reset the Hello interval: no ip hello-interval eigrp as# Hello interval depends on the interface’s bandwidth.• High bandwidth = 5 seconds• Default interval on point-to-point serial links, multipoint circuits withbandwidth greater than T1, and LANs.• Low Bandwidth = 60 seconds• Default interval on T1 or less multipoint WAN circuits.
  • Chapter 224© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicHello Packets On hearing Hellos, a router creates a neighbor table andthe continued receipt of Hellos maintains the table. Holdtime is the maximum amount of allowed time thatHellos are not heard from a neighbor.• Three times the Hello Interval:• Low Bandwidth (3 x 60 sec.) = 180 seconds• High bandwidth (3 x 5 sec.) = 15 seconds
  • Chapter 225© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicHello PacketsT3
  • Chapter 226© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicAcknowledgement Packets Are used to indicate receipt of any EIGRP packet during a"reliable" (i.e., RTP) exchange.• To be reliable, a senders message must be acknowledged by therecipient. Acknowledgment packets are:• Dataless Hello packets.• Unicast.
  • Chapter 227© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicUpdate Packets After the local router discovers a new neighbor, updatepackets are sent to the new neighbor. Update packets are also used when a router detects atopology change.• The router sends a multicast Update packet to all neighbors, alertingthem to the change. All Update packets are sent reliably.
  • Chapter 228© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicUpdate PacketsUpdate packet• Initially sent after a new neighbor is discovered.• Sent when a topology change has been detected.
  • Chapter 229© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicQuery and Reply Packets Query and Reply packets are sent when a destination hasno feasible successors. Both packet types are sent reliably. A Query packet is multicasted to other EIGRP routersduring the route re-computation process.• Query packets are always multicast. A Reply packet is used to respond to a query to instruct theoriginator not to recompute the route because feasiblesuccessors exist.• Reply packets are always unicast.
  • Chapter 230© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicQuery and Reply Packets
  • Chapter 231© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Message
  • Chapter 232© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Message - TLVs
  • Chapter 233© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicTLV 0x0001 - EIGRP Parameters• K values are used to calculate the EIGRP metric.• The Hold Time advertised by a neighbor is the maximumtime a router should wait for any valid EIGRP message sentby that neighbor before declaring it dead.
  • Chapter 234© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicTLV 0x0002 - Internal IP Routes• Delay: Sum of delays in units of10 microseconds from source todestination.• Bandwidth: Lowest configuredbandwidth on any interface alongthe route.• Prefix length: Specifies thenumber of network bits in thesubnet mask.• Destination: The destinationaddress of the route.
  • Chapter 235© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicTLV 0x0003 - External IP Routes IP external routes are routes which are imported into EIGRPthrough redistribution of a default route or other routing protocols.• Fields used to trackexternal source of route.• Same fields contained inthe Internal IP route TLV(0x0002).
  • Chapter 236© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicPacket TypesPacket Type UseHello Used to discover other EIGRP routers in thenetwork.Acknowledgement Used to acknowledge the receipt of any EIGRPpacket.Update Convey routing information to knowndestinations.Query Used to get specific information from a neighborrouter.Reply Used to respond to a query.
  • Chapter 237© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicInitial Route Discovery
  • Chapter 238© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Operations EIGRP selects primary (successor) and backup (feasible successor)routes and injects those into the topology table. The primary (successor) routes are then moved to the routing table.IP EIGRP Neighbor TableNeighbor IP Address Local router exitinterface to neighborIP EIGRP Topology TableDestination 1 FD / AD via each neighborIP Routing TableDestination 1 Best routeList of directly connected adjacent EIGRPneighbor routers and the local interface to exitto reach it.List of all routes learned from each EIGRPneighbor and identifies successor routes andfeasible successor routes.List of the best (successor) routes from theEIGRP topology table and other routingprocesses.
  • Chapter 239© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicExample: EIGRP TablesRouter C’s tables:
  • Chapter 240© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicR1# show ip eigrp neighborsIP-EIGRP neighbors for process 100H Address Interface Hold Uptime SRTT RTO Q Seq(sec) (ms) Cnt Num0 192.168.1.102 Se0/0/1 11 00:07:22 10 2280 0 5R1#EIGRP Neighbor TableLists the order inwhich a peeringsession wasestablished withthe specifiedneighbor, startingwith 0.Neighbor’sIP addressLocal interfacereceiving EIGRPHello packets.Seconds remaining before declaring neighbordown.The current hold time and is reset to themaximum hold time whenever a Hello packetis received.SRTT (Smooth Round Trip Timer) and RTO (Retransmit Interval) are used byRTP to manage reliable EIGRP packets.SRTT indicates how long it takes for this neighbor to respond to reliablepackets.RTO indicates how long to wait before retransmitting if no ACK is received.Queue countshould always bezero otherwisethere’scongestion on thelink.The sequencenumber of thelast update,query, or replypacket that wasreceived fromthis neighbor.Amount of timesince thisneighbor wasadded to theneighbor table.
  • Chapter 241© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicR1# show ip eigrp topologyIP-EIGRP Topology Table for AS(100)/ID(192.168.1.101)Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,r - reply Status, s - sia StatusP 172.17.0.0/16, 1 successors, FD is 40514560via 192.168.1.102 (40514560/28160), Serial0/0/1R1#EIGRP Topology TableIndicates if theroute is in passiveor active state.Destination network. Number ofsuccessorsNext-hop addressfor successor.Outbound interfaceto reach the network.Feasible distance (FD)to the successorFeasibledistance (FD)to thesuccessorAdvertiseddistance (AD)from thesuccessor
  • Chapter 242© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Routing TableEIGRProuteDestinationnetworkR1# show ip route<output omitted>Gateway of last resort is not setD 172.17.0.0/16 [90/40514560] via 192.168.1.102, 00:02:22, Serial0/0/1172.16.0.0/16 is variably subnetted, 2 subnets, 2 masksD 172.16.0.0/16 is a summary, 00:31:31, Null0C 172.16.1.0/24 is directly connected, FastEthernet0/0R1#AdministrativedistanceFeasibledistanceNext-hop addressto reach thenetworkTime indicatingthe last updatepacket receivedLocal router exitinterface todestinationnetworkSummary route automatically created as the resultof the default classful behavior of EIGRP.
  • Chapter 243© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Administrative Distance (AD) EIGRP default administrative distancesRoutes manuallysummarized.Routes redistributed intoEIGRP.
  • Chapter 244© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicDUAL Example(1)10.1.1.0 /24ACBED(2) (2) (1)(1)(1)EIGRP FD AD Topology10.1.1.0 /24 3 ***** Passive *****via B 3 1 Successorvia D 4 2 Feasible Successorvia E 4 3Router CEIGRP FD AD Topology10.1.1.0 /24 3 ***** Passive *****via D 3 2 Successorvia C 4 3Router EEIGRP FD AD Topology10.1.1.0 /24 2 ***** Passive *****via B 2 1 Successorvia C 5 3Router D
  • Chapter 245© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicDUAL Example(1)10.1.1.0 /24ACBED(2) (2) (1)(1)(1)EIGRP FD AD Topology10.1.1.0 /24 3 ***** Passive *****via B 3 1 Successorvia D 4 2 Feasible Successorvia E 4 3Router CEIGRP FD AD Topology10.1.1.0 /24 3 ***** Passive *****via D 3 2 Successorvia C 4 3Router EEIGRP FD AD Topology10.1.1.0 /24 2 ***** Passive *****via B 2 1 Successorvia C 5 3Router D
  • Chapter 246© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicDUAL Example(1)10.1.1.0 /24ACBED(2) (2) (1)(1)EIGRP FD AD Topology10.1.1.0 /24 3 ***** Passive *****via B 3 1 Successorvia D 4 2 Feasible Successorvia E 4 3Router CEIGRP FD AD Topology10.1.1.0 /24 3 ***** Passive *****via D 3 2 Successorvia C 4 3Router EEIGRP FD AD Topology10.1.1.0 /24 -1 ***** ACTIVE ******via E (Q) Queryvia C 5 3 (Q) QueryRouter DQQ Q = Query
  • Chapter 247© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicDUAL Example(1)10.1.1.0 /24ACBED(2) (2) (1)(1)EIGRP FD AD Topology10.1.1.0 /24 3 ***** Passive *****via B 3 1 Successorvia Dvia E 4 3Router CEIGRP FD AD Topology10.1.1.0 /24 -1 ***** ACTIVE ******via Dvia C 4 3 (Q) QueryRouter EEIGRP FD AD Topology10.1.1.0 /24 -1 ***** ACTIVE ******via E (Q) Queryvia C 5 3Router DRQQ = QueryR = Reply
  • Chapter 248© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicDUAL Example(1)10.1.1.0 /24ACBED(2) (2) (1)(1)EIGRP FD AD Topology10.1.1.0 /24 3 ***** Passive *****via B 3 1 Successorvia Dvia ERouter CEIGRP FD AD Topology10.1.1.0 /24 4 ***** Passive *****via C 4 3 Successorvia DRouter EEIGRP FD AD Topology10.1.1.0 /24 -1 ***** ACTIVE ******via E (Q) Queryvia C 5 3Router DRQ = QueryR = Reply
  • Chapter 249© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicDUAL Example(1)10.1.1.0 /24ACBED(2) (2) (1)(1)EIGRP FD AD Topology10.1.1.0 /24 3 ***** Passive *****via B 3 1 Successorvia Dvia ERouter CEIGRP FD AD Topology10.1.1.0 /24 4 ***** Passive *****via C 4 3 Successorvia DRouter EEIGRP FD AD Topology10.1.1.0 /24 5 ***** Passive *****via C 5 3 Successorvia E 5 4 SuccessorRouter DRQ = QueryR = Reply
  • Chapter 250© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicDUAL Example(1)10.1.1.0 /24ACBED(2) (2) (1)(1)EIGRP FD AD Topology10.1.1.0 /24 3 ***** Passive *****via B 3 1 Successorvia Dvia ERouter CEIGRP FD AD Topology10.1.1.0 /24 4 ***** Passive *****via C 4 3 Successorvia DRouter EEIGRP FD AD Topology10.1.1.0 /24 5 ***** Passive *****via C 5 3 Successorvia E 5 4 SuccessorRouter D
  • Chapter 251© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Metric Calculation EIGRP uses a composite metric which can be based on thefollowing metrics:• Bandwidth• Delay• Reliability• Load Only Bandwidth and Delay are used by default.Note: It is often incorrectly stated that EIGRP can also use the smallestMTU in the path. In actual fact, the MTU is included in the EIGRP routingupdate, but is not actually used in the metric calculation.
  • Chapter 252© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Bandwidth EIGRP uses the slowest bandwidth (BW) in its metriccalculation.• Calculated BW = reference BW / slowest BW (kbps) The value of the bandwidth may or may not reflect theactual physical bandwidth of the interface.• For example, most serial interfaces use the default bandwidth value of1.544 Mbps but this may not accurately reflect the links actualbandwidth.
  • Chapter 253© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Bandwidth Because both EIGRP and OSPF use bandwidth in defaultmetric calculations, a correct value for bandwidth is veryimportant to the accuracy of routing information.• If the actual bandwidth of the link differs from the default bandwidthvalue, then the bandwidth value should be modified. To modify the bandwidth value, use the bandwidthinterface command.Note: The bandwidth command does NOT change the physical bandwidthof the link.
  • Chapter 254© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Delay Delay is a measure of thetime it takes for a packet totraverse a route.• EIGRP uses the cumulativesum of all outgoing interfaces.• Calculated Delay = the sum ofoutgoing interface delays / 10 The delay (DLY) metric isa static value based on thetype of link to which theinterface is connected andis expressed inmicroseconds.
  • Chapter 255© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicOther EIGRP Metrics Reliability (not a default EIGRP metric) is a measure of thelikelihood that a link will fail.• Measure dynamically & expressed as a fraction of 255.• The higher the fraction the better the reliability Load (not a default EIGRP metric) reflects how much trafficis using a link• Number is determined dynamically and is expressed as a fraction of255• The lower the fraction the less the load on the link These optional criteria can be used but are notrecommended, because they typically result in frequentrecalculation of the topology table.
  • Chapter 256© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Composite Metric Calculation The EIGRP composite metric formula consists of values K1through K5, known as EIGRP metric weights.• By default, only K1 (bandwidth) and K3 (delay) are set to 1.• K2 (load), K4 (reliability), and K5 (MTU) are set to 0. K values can be changed with the EIGRP router command:Router(config-router)# metric weights tos k1 k2 k3k4 k5
  • Chapter 257© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicMismatched K Values EIGRP neighbors cannot use mismatched metric values.• All EIGRP neighbors must use the same metrics.• Metrics can be altered using the metric weights command.
  • Chapter 258© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Metric Calculation ExampleSlowest bandwidth:Plus the sum of the delays
  • Chapter 259© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Bandwidth Calculation Example Bandwidth = 10,000,000 / 1024 = 9765 * 256 = 2499840
  • Chapter 260© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Delay Calculation Example Delay = 20,000 / 10 + (100 / 10) * 256 = 514560
  • Chapter 261© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Metric Calculation Example EIGRP Metric = 2499840 + 514560 = 3014400
  • Chapter 262© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicPlanning EIGRPRoutingImplementations
  • Chapter 263© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicPlanning to Deploy EIGRP Prior to deploying an EIGRP routing solution, the followingshould be considered:• IP addressing plan• Network topology• EIGRP traffic engineering Once the requirements have been assessed, theimplementation plan can be created.
  • Chapter 264© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicImplementing EIGRP The information necessary to implement EIGRP routingincludes the following:• The IP addresses to be configured on individual router interfaces• The EIGRP AS number, used to enable EIGRP.• A list of routers and interfaces on which EIGRP is to be enabled.• Metrics that need to be applied to specific interfaces, or EIGRP trafficengineering. In the implementation plan, EIGRP the tasks include thefollowing:• Enabling the EIGRP routing protocol.• Configuring the proper network statements.• Optionally configuring the metric to appropriate interfaces.
  • Chapter 265© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicVerifying EIGRP After implementing EIGRP, verification should confirmproper deployment on each router. Verification tasks include verifying:• The EIGRP neighbor relationships.• That the EIGRP topology table is populated with the necessaryinformation.• That IP routing table is populated with the necessary information.• That there is connectivity in the network between routers and to otherdevices.• That EIGRP behaves as expected in a case of a topology change, bytesting link failure and router failure events.
  • Chapter 266© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicDocumenting After a successful EIGRP deployment, the solution andverification process and results should be documented forfuture reference. Documentation should include:• A topology map• The IP addressing plan• The AS number used• The networks included in EIGRP on each router• Any special metrics configured
  • Chapter 267© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicConfiguring andVerifying EIGRP
  • Chapter 268© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEnable EIGRP Routing Define EIGRP as the IP routing protocol.Router(config)#router eigrp autonomous-system-id To exchange routing updates, EIGRP routers musthave the same autonomous system ID.
  • Chapter 269© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicIdentify EIGRP Networks Define EIGRP networks to advertise to EIGRP neighbors.Router(config-router)#network network [mask] The network parameter can be a network, a subnet, or theaddress of a directly connected interface. The mask is a wildcard mask (inverse mask) used todetermine how to interpret the address.• The mask has wildcard bits, where 0 is a match and 1 is ―don’tcare.‖• For example, 0.0.255.255 indicates a match in the first 2 octets.
  • Chapter 270© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicNote on EIGRP Masks Most EIGRP references state that the wildcard mask isrequired. However, since IOS 12.0(4)T, the mask argument canactually be configured using wild card bits or a regularsubnet mask. For example, either format could be used to configure the10.10.10.0 network:network 10.10.10.0 0.0.0.3ornetwork 10.10.10.0 255.255.255.252
  • Chapter 271© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicDefine the Interface Bandwidth Defines the interface’s bandwidth (optional).Router(config-if)#bandwidth kilobits The kilobits parameter indicates the intendedbandwidth in kbps. For example, to set the bandwidth to 512,000 bps, use thebandwidth 512 command. The configured bandwidth is used by routing protocols inthe metric calculation. The command does not actually change the speed of theinterface.
  • Chapter 272© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEnable / Disable Automatic Summarization By default, EIGRP automatically summarizes subnets.Router(config-router)#auto-summary This makes EIGRP behave like a classful routing protocoland therefore summarizes subnets on the classfulboundary. Automatic summarization can be disabled using the noauto-summary router configuration command.
  • Chapter 273© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicConfiguring EIGRP Example: ClassfulR1(config)# interface Fa0/0R1(config-if)# ip address 172.16.1.1 255.255.255.0R1(config-if)# no shutR1(config-if)# interface S0/0/0R1(config-if)# ip address 192.168.1.101 255.255.255.224R1(config-if)# bandwidth 64R1(config-if)# no shutR1(config-if)# exitClassful configuration example:R2(config)# interface Fa0/0R2(config-if)# ip address 172.16.2.1 255.255.255.0R2(config-if)# no shutR2(config-if)# interface S0/0/0R2(config-if)# ip address 192.168.1.102 255.255.255.224R2(config-if)# bandwidth 64R2(config-if)# no shutR2(config-if)# interface S0/0/1R2(config-if)# ip address 192.168.1.1 255.255.255.224R2(config-if)# bandwidth 64R2(config-if)# no shutR2(config-if)# exitFa0/0Fa0/0R1 R2172.16.1.0 /24EIGRP AS 100Internet192.168.1.0 /27S0/0/1172.17.2.0 /24S0/0/0S0/0/064 kbps192.168.1.96 /27.101.102 .1.1.1
  • Chapter 274© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicConfiguring EIGRP Example: ClassfulR1(config)# router eigrp 100R1(config-router)# network 192.168.1.96R1(config-router)# network 172.16.1.0R1(config-router)#Classful configuration example:R2(config)# router eigrp 100R2(config-router)# network 192.168.1.96R2(config-router)# network 172.17.2.0*Jul 26 10:02:25.963: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 192.168.1.101 (Serial0/0/0) isup: new adjacency 172.17.2.0R2(config-router)#R2#Fa0/0Fa0/0R1 R2172.16.1.0 /24EIGRP AS 100Internet192.168.1.0 /27S0/0/1172.17.2.0 /24S0/0/0S0/0/064 kbps192.168.1.96 /27.101.102 .1.1.1
  • Chapter 275© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicVerifying EIGRP ExampleR1# show running-config | section router eigrprouter eigrp 100network 172.16.0.0network 192.168.1.0auto-summaryR1# show ip route<output omitted>Gateway of last resort is not setD 172.17.0.0/16 [90/40514560] via 192.168.1.102, 00:24:02, Serial0/0/0172.16.0.0/16 is variably subnetted, 2 subnets, 2 masksD 172.16.0.0/16 is a summary, 00:25:27, Null0C 172.16.1.0/24 is directly connected, FastEthernet0/0192.168.1.0/24 is variably subnetted, 3 subnets, 2 masksC 192.168.1.96/27 is directly connected, Serial0/0/0D 192.168.1.0/27 [90/41024000] via 192.168.1.102, 00:16:56, Serial0/0/0D 192.168.1.0/24 is a summary, 00:25:27, Null0R1#Classful configuration example:Fa0/0Fa0/0R1 R2172.16.1.0 /24EIGRP AS 100Internet192.168.1.0 /27S0/0/1172.17.2.0 /24S0/0/0S0/0/064 kbps192.168.1.96 /27.101.102 .1.1.1
  • Chapter 276© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicVerifying EIGRP ExampleR2# show running-config | section router eigrprouter eigrp 100network 172.17.0.0network 192.168.1.0auto-summaryR2# show ip route<output omitted>Gateway of last resort is not set172.17.0.0/16 is variably subnetted, 2 subnets, 2 masksD 172.17.0.0/16 is a summary, 00:13:10, Null0C 172.17.2.0/24 is directly connected, FastEthernet0/0D 172.16.0.0/16 [90/40514560] via 192.168.1.101, 00:13:26, Serial0/0/0192.168.1.0/24 is variably subnetted, 3 subnets, 2 masksC 192.168.1.96/27 is directly connected, Serial0/0/0C 192.168.1.0/27 is directly connected, Serial0/0/1D 192.168.1.0/24 is a summary, 00:13:10, Null0R2#Classful configuration example:Fa0/0Fa0/0R1 R2172.16.1.0 /24EIGRP AS 100Internet192.168.1.0 /27S0/0/1172.17.2.0 /24S0/0/0S0/0/064 kbps192.168.1.96 /27.101.102 .1.1.1
  • Chapter 277© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicVerifying EIGRP ExampleR2# show ip protocolsRouting Protocol is "eigrp 100"<output omitted>Automatic network summarization is in effectAutomatic address summarization:192.168.1.0/24 for FastEthernet0/0Summarizing with metric 40512000172.17.0.0/16 for Serial0/0/0, Serial0/0/1Summarizing with metric 28160Maximum path: 4Routing for Networks:172.17.0.0192.168.1.0Routing Information Sources:<output omitted>R2#Classful configuration example:Fa0/0Fa0/0R1 R2172.16.1.0 /24EIGRP AS 100Internet192.168.1.0 /27S0/0/1172.17.2.0 /24S0/0/0S0/0/064 kbps192.168.1.96 /27.101.102 .1.1.1
  • Chapter 278© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicConfiguring EIGRP Example: ClasslessClassless configuration example:R2(config)# no router eigrp 100R2(config)# router eigrp 100R2(config-router)# network 192.168.1.96 0.0.0.31R2(config-router)# network 172.17.2.0 0.0.0.255R2(config-router)# endR2# show run | section router eigrprouter eigrp 100network 172.17.2.0 0.0.0.255network 192.168.1.96 0.0.0.31auto-summaryR2#Fa0/0Fa0/0172.17.2.0 /24R1 R2172.16.1.0 /24EIGRP AS 100Internet192.168.1.0 /2764 kbps192.168.1.96 /27.101.102S0/0/1S0/0/0S0/0/0.1.1.1R1(config)# no router eigrp 100R1(config)# router eigrp 100R1(config-router)# network 192.168.1.96 0.0.0.31R1(config-router)# network 172.16.1.0 0.0.0.255R1(config-router)# endR1# show run | section router eigrprouter eigrp 100network 172.16.1.0 0.0.0.255network 192.168.1.96 0.0.0.31auto-summaryR1#
  • Chapter 279© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicVerifying EIGRP ExampleR2# show ip protocolsRouting Protocol is "eigrp 100"<output omitted>Automatic network summarization is in effectAutomatic address summarization:192.168.1.0/24 for FastEthernet0/0Summarizing with metric 40512000172.17.0.0/16 for Serial0/0/0Summarizing with metric 28160Maximum path: 4Routing for Networks:172.17.2.0/24192.168.1.96/27Routing Information Sources:Gateway Distance Last Update(this router) 90 00:00:06Gateway Distance Last Update192.168.1.101 90 00:00:26Distance: internal 90 external 170Classful configuration example:Fa0/0Fa0/0R1 R2172.16.1.0 /24EIGRP AS 100Internet192.168.1.0 /27S0/0/1172.17.2.0 /24S0/0/0S0/0/064 kbps192.168.1.96 /27.101.102 .1.1.1
  • Chapter 280© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicVerifying EIGRP: show ip protocolsR1# show ip protocolsRouting Protocol is "eigrp 100"<output omitted>EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0EIGRP maximum hopcount 100EIGRP maximum metric variance 1Redistributing: eigrp 100EIGRP NSF-aware route hold timer is 240sAutomatic network summarization is in effectAutomatic address summarization:192.168.1.0/24 for FastEthernet0/0Summarizing with metric 40512000172.16.0.0/16 for Serial0/0/0Summarizing with metric 28160Maximum path: 4Routing for Networks:172.16.1.0/24192.168.1.96/27Routing Information Sources:Gateway Distance Last Update(this router) 90 00:08:56Gateway Distance Last Update192.168.1.102 90 00:07:59Distance: internal 90 external 170Verify routing protocol information on the router.
  • Chapter 281© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicVerifying EIGRP: show ip eigrp neighborsR1# show ip eigrp neighborsIP-EIGRP neighbors for process 100H Address Interface Hold Uptime SRTT RTO Q Seq(sec) (ms) Cnt Num0 192.168.1.102 Se0/0/0 11 00:09:17 22 2280 0 5R1#EIGRP uses the Neighbor table to list adjacent routers.
  • Chapter 282© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicVerifying EIGRP: show ip eigrp topologyR1# show ip eigrp topologyIP-EIGRP Topology Table for AS(100)/ID(192.168.1.101)Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,r - reply Status, s - sia StatusP 192.168.1.96/27, 1 successors, FD is 40512000via Connected, Serial0/0/0P 192.168.1.0/24, 1 successors, FD is 40512000via Summary (40512000/0), Null0P 172.16.0.0/16, 1 successors, FD is 28160via Summary (28160/0), Null0P 172.17.0.0/16, 1 successors, FD is 40514560via 192.168.1.102 (40514560/28160), Serial0/0/0P 172.16.1.0/24, 1 successors, FD is 28160via Connected, FastEthernet0/0R1#Verify routing protocol information on the router.
  • Chapter 283© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicVerifying EIGRP: show ip route eigrpR1# show ip route eigrpD 172.17.0.0/16 [90/40514560] via 192.168.1.102, 00:10:18, Serial0/0/0172.16.0.0/16 is variably subnetted, 2 subnets, 2 masksD 172.16.0.0/16 is a summary, 00:11:19, Null0192.168.1.0/24 is variably subnetted, 2 subnets, 2 masksD 192.168.1.0/24 is a summary, 00:11:19, Null0R1#R1# show ip route<output omitted>Gateway of last resort is not setD 172.17.0.0/16 [90/40514560] via 192.168.1.102, 00:10:35, Serial0/0/0172.16.0.0/16 is variably subnetted, 2 subnets, 2 masksD 172.16.0.0/16 is a summary, 00:11:37, Null0C 172.16.1.0/24 is directly connected, FastEthernet0/0192.168.1.0/24 is variably subnetted, 2 subnets, 2 masksC 192.168.1.96/27 is directly connected, Serial0/0/0D 192.168.1.0/24 is a summary, 00:11:37, Null0R1#Verify that the router recognizes EIGRP routes.
  • Chapter 284© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicVerifying EIGRP: show ip eigrp interfacesR1# show ip eigrp interfacesIP-EIGRP interfaces for process 100Xmit Queue Mean Pacing Time Multicast PendingInterface Peers Un/Reliable SRTT Un/Reliable Flow Timer RoutesSe0/0/0 1 0/0 22 10/380 468 0Fa0/0 0 0/0 0 0/1 0 0R1#Verify EIGRP configured interfaces.
  • Chapter 285© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicVerifying EIGRP: show ip eigrp trafficR1# show ip eigrp trafficIP-EIGRP Traffic Statistics for AS 100Hellos sent/received: 338/166Updates sent/received: 7/7Queries sent/received: 0/0Replies sent/received: 0/0Acks sent/received: 2/2SIA-Queries sent/received: 0/0SIA-Replies sent/received: 0/0Hello Process ID: 228PDM Process ID: 226IP Socket queue: 0/2000/1/0 (current/max/highest/drops)Eigrp input queue: 0/2000/1/0 (current/max/highest/drops)R1#Verify EIGRP traffic information.
  • Chapter 286© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicVerifying EIGRP: debug eigrp packetsR2# debug eigrp packets*Jul 26 10:51:24.051: EIGRP: Sending HELLO on Serial0/0/0*Jul 26 10:51:24.051: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0*Jul 26 10:51:24.111: EIGRP: Sending HELLO on FastEthernet0/0*Jul 26 10:51:24.111: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0*Jul 26 10:51:26.667: EIGRP: Received HELLO on Serial0/0/0 nbr 192.168.1.101*Jul 26 10:51:26.667: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0*Jul 26 10:51:28.451: EIGRP: Sending HELLO on FastEthernet0/0*Jul 26 10:51:28.451: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0*Jul 26 10:51:29.027: EIGRP: Sending HELLO on Serial0/0/0*Jul 26 10:51:29.027: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0*Jul 26 10:51:31.383: EIGRP: Received HELLO on Serial0/0/0 nbr 192.168.1.101*Jul 26 10:51:31.383: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0*Jul 26 10:51:33.339: EIGRP: Sending HELLO on FastEthernet0/0*Jul 26 10:51:33.339: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0*Jul 26 10:51:33.511: EIGRP: Sending HELLO on Serial0/0/0*Jul 26 10:51:33.511: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0*Jul 26 10:51:36.347: EIGRP: Received HELLO on Serial0/0/0 nbr 192.168.1.101*Jul 26 10:51:36.347: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0*Jul 26 10:51:37.847: EIGRP: Sending HELLO on Serial0/0/0*Jul 26 10:51:37.847: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0*Jul 26 10:51:37.899: EIGRP: Sending HELLO on FastEthernet0/0Traces transmission and receipt of EIGRP packets.
  • Chapter 287© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Passive-Interface Prevent EIGRP updates out a specified router interface.Router(config-router)#passive-interface type number [default] Set a particular interface or all router interfaces to passive. The default option sets all router interfaces to passive. For EIGRP, the command: Prevents neighbor relationships from being established. Routing updates from a neighbor are ignored. Allows a subnet on a passive interface to be announced in EIGRP
  • Chapter 288© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicPassive-Interface ExampleR1(config)# router eigrp 100R1(config-router)# passive-interface fa0/0R1(config-router)#R2(config)# router eigrp 100R2(config-router)# passive-interface fa0/0R2(config-router)#Alternate configuration:R1(config)# router eigrp 100R1(config-router)# passive-interface defaultR1(config-router)# no passive-interface S0/0/0R2(config)# router eigrp 100R2(config-router)# passive-interface defaultR2(config-router)# no passive-interface S0/0/0Fa0/0Fa0/0R1 R2172.16.1.0 /24EIGRP AS 100Internet192.168.1.0 /27172.17.2.0 /2464 kbps192.168.1.96 /27.101.102S0/0/1S0/0/0S0/0/0.1.1.1
  • Chapter 289© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicPropagating a Default Route To propagate a default route in EIGRP, use either the:ip default-network network-number global configurationcommand.Orip route 0.0.0.0 0.0.0.0 next-hop | interface routerconfiguration command. Once configured, the default route has to be propagatedinto the EIGRP AS.
  • Chapter 290© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Publicip default-network Command Configures a router to advertise a network as the gateway of lastresort.Router(config)#ip default-network network Other routers use their next-hop address to the advertised network astheir default route. There is no parameter to specify the subnet mask therefore thecommand can only be used to advertise a classful network. The specified network must be reachable before it is configured. If the specified network is reachable through: EIGRP, then the default route is propagated automatically to other EIGRProuters in the AS. A static route, then the static route must be redistributed into EIGRP.
  • Chapter 291© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Publicip default-network ExampleR2# show ip route<output omitted>Gateway of last resort is not set172.17.0.0/16 is variably subnetted, 2 subnets, 2 masksD 172.17.0.0/16 is a summary, 02:27:56, Null0C 172.17.2.0/24 is directly connected, FastEthernet0/0D 172.16.0.0/16 [90/40514560] via 192.168.1.101, 02:27:56, Serial0/0/0192.168.1.0/27 is subnetted, 2 subnetsC 192.168.1.96 is directly connected, Serial0/0/0C 192.168.1.0 is directly connected, Serial0/0/1R2#R1# show ip route<output omitted>Gateway of last resort is not set<output omitted>Fa0/0Fa0/0R1 R2172.16.1.0 /2464 kbpsEIGRP AS 100Internet172.31.0.0 /16192.168.1.96 /27172.17.2.0 /24.101.102S0/0/1S0/0/0S0/0/0.1.1.1192.168.1.0 /27.2
  • Chapter 292© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Publicip default-network ExampleFa0/0Fa0/0R1 R2172.16.1.0 /2464 kbpsEIGRP AS 100Internet172.31.0.0 /16192.168.1.96 /27172.17.2.0 /24.101.102S0/0/1S0/0/0S0/0/0.1.1.1192.168.1.0 /27.2R2(config)# ip route 172.31.0.0 255.255.0.0 192.168.1.2R2(config)# do ping 172.31.0.0<output omitted>Success rate is 100 percent (5/5), round-trip min/avg/max = 28/28/28 msR2(config)# ip default-network 172.31.0.0R2(config)# router eigrp 100R2(config-router)# redistribute staticR2(config-router)# endR2#
  • Chapter 293© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Publicip default-network ExampleR2# show ip route<output omitted>Gateway of last resort is 192.168.1.2 to network 172.31.0.0<output omitted>S* 172.31.0.0/16 [1/0] via 192.168.1.2192.168.1.0/27 is subnetted, 2 subnetsC 192.168.1.96 is directly connected, Serial0/0/0C 192.168.1.0 is directly connected, Serial0/0/1R2#Fa0/0Fa0/0R1 R2172.16.1.0 /2464 kbpsEIGRP AS 100Internet172.31.0.0 /16192.168.1.96 /27172.17.2.0 /24.101.102S0/0/1S0/0/0S0/0/0.1.1.1192.168.1.0 /27.2R1# show ip route<output omitted>Gateway of last resort is 192.168.1.102 to network 172.31.0.0<output omitted.D*EX 172.31.0.0/16 [170/41024000] via 192.168.1.102, 00:00:20, Serial0/0/0192.168.1.0/27 is subnetted, 1 subnetsC 192.168.1.96 is directly connected, Serial0/0/0R1#
  • Chapter 294© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Publicip route 0.0.0.0 0.0.0.0 next-hop |interface Command Configures a router to advertise a default route as the gateway of lastresort.Router(config)#ip route 0.0.0.0 0.0.0.0 interface | next-hop The choice of parameter affects the next selection of commands. If the interface parameter is used, then only the network 0.0.0.0needs to also be entered. If the next-hop parameter is used, then the network 0.0.0.0 andthe redistribute static command must be configured.
  • Chapter 295© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Publicip route 0.0.0.0 0.0.0.0 interfaceExampleFa0/0Fa0/0R1 R2172.16.1.0 /2464 kbpsEIGRP AS 100Internet172.31.0.0 /16192.168.1.96 /27172.17.2.0 /24.101.102S0/0/1S0/0/0S0/0/0.1.1.1192.168.1.0 /27.2R2(config)# ip route 0.0.0.0 0.0.0.0 S0/0/1R2(config)# router eigrp 100R2(config-router)# network 0.0.0.0R2(config-router)# do show ip route<output omitted>Gateway of last resort is 0.0.0.0 to network 0.0.0.0172.17.0.0/16 is variably subnetted, 2 subnets, 2 masksD 172.17.0.0/16 is a summary, 03:13:25, Null0C 172.17.2.0/24 is directly connected, FastEthernet0/0D 172.16.0.0/16 [90/40514560] via 192.168.1.101, 03:13:25, Serial0/0/0192.168.1.0/27 is subnetted, 2 subnetsC 192.168.1.96 is directly connected, Serial0/0/0C 192.168.1.0 is directly connected, Serial0/0/1S* 0.0.0.0/0 is directly connected, Serial0/0/1R2(config-router)#
  • Chapter 296© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Publicip route 0.0.0.0 0.0.0.0 next-hopExampleFa0/0Fa0/0R1 R2172.16.1.0 /2464 kbpsEIGRP AS 100Internet172.31.0.0 /16192.168.1.96 /27172.17.2.0 /24.101.102S0/0/1S0/0/0S0/0/0.1.1.1192.168.1.0 /27.2R2(config)# ip route 0.0.0.0 0.0.0.0 192.168.1.2R2(config)# router eigrp 100R2(config-router)# network 0.0.0.0R2(config-router)# redistribute staticR2(config-router)# do show ip route<output omitted>Gateway of last resort is 192.168.1.2 to network 0.0.0.0172.17.0.0/16 is variably subnetted, 2 subnets, 2 masksD 172.17.0.0/16 is a summary, 02:53:48, Null0C 172.17.2.0/24 is directly connected, FastEthernet0/0D 172.16.0.0/16 [90/40514560] via 192.168.1.101, 02:53:48, Serial0/0/0192.168.1.0/27 is subnetted, 2 subnetsC 192.168.1.96 is directly connected, Serial0/0/0C 192.168.1.0 is directly connected, Serial0/0/1S* 0.0.0.0/0 [1/0] via 192.168.1.2R2(config-router)#
  • Chapter 297© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Route Summarization EIGRP automatically summarizes routes at a major networkboundary by default.• Due to the pre-configured auto-summary router configurationcommand.• In most cases, auto summarization is a good thing as it keeps routingtables as compact as possible.• Sometimes it’s not a good thing such as when there is adiscontiguous subnetwork. Typically for routing to work properly, auto-summarizationshould be disabled using the no auto-summary routerconfiguration command.
  • Chapter 298© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicSummarization in Discontiguous NetworksR1 R210.10.10.0 /24EIGRP AS 100192.168.1.96 /30 10.20.20.0 /24 EIGRP Update: Connected to 10.0.0.0 /8R1# show running-config | section router eigrprouter eigrp 100passive-interface FastEthernet0/0network 10.10.10.0 0.0.0.255network 192.168.1.96 0.0.0.31auto-summaryR1# show ip protocolsRouting Protocol is "eigrp 100"<output omitted>Automatic network summarization is in effectAutomatic address summarization:10.0.0.0/8 for Serial0/0/0Summarizing with metric 28160Maximum path: 4Routing for Networks:10.10.10.0/24192.168.1.96/27Passive Interface(s):FastEthernet0/0<output omitted>
  • Chapter 299© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicSummarization in Discontiguous NetworksR2# show ip route<output omitted>Gateway of last resort is 192.168.1.2 to network 0.0.0.010.0.0.0/8 is variably subnetted, 2 subnets, 2 masksC 10.20.20.0/24 is directly connected, FastEthernet0/0D 10.0.0.0/8 is a summary, 00:13:35, Null0192.168.1.0/27 is subnetted, 2 subnetsC 192.168.1.96 is directly connected, Serial0/0/0C 192.168.1.0 is directly connected, Serial0/0/1S* 0.0.0.0/0 [1/0] via 192.168.1.2R2#R1 R210.10.10.0 /24EIGRP AS 100192.168.1.96 /30 10.20.20.0 /24 EIGRP Update: Connected to 10.0.0.0 /8R2 ignores the R1 updatebecause it is alreadyconnected to the classful10.0.0.0/8 network.
  • Chapter 2100© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicNull 0 Notice that the summarized route (10.0.0.0/8) has an entrypointing to null0.• Null0 is automatically added to the table and are called summaryroutes.• Null 0 is a directly connected, software-only interface.• The use of the null0 interface prevents the router from trying toforward traffic to other routers in search of a more precise, longermatch.R2# show ip route<output omitted>Gateway of last resort is 192.168.1.2 to network 0.0.0.010.0.0.0/8 is variably subnetted, 2 subnets, 2 masksC 10.20.20.0/24 is directly connected, FastEthernet0/0D 10.0.0.0/8 is a summary, 00:13:35, Null0192.168.1.0/27 is subnetted, 2 subnetsC 192.168.1.96 is directly connected, Serial0/0/0C 192.168.1.0 is directly connected, Serial0/0/1S* 0.0.0.0/0 [1/0] via 192.168.1.2R2#
  • Chapter 2101© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicDisabling Automatic SummarizationR1 R210.10.10.0 /24EIGRP AS 100192.168.1.96 /30 10.20.20.0 /24 EIGRP Update: Connected to 10.0.0.0 /8R1(config)# router eigrp 100R1(config-router)# no auto-summaryR1(config-router)#*Jul 26 22:14:07.183: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 192.168.1.102(Serial0/0/0) is resync: summary configuredR1(config-router)# endR1# show ip protocolsRouting Protocol is "eigrp 100“<output omitted>Automatic network summarization is not in effectMaximum path: 4Routing for Networks:10.10.10.0/24192.168.1.96/27<output omitted>
  • Chapter 2102© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicDisable Automatic SummarizationR1 R210.10.10.0 /24EIGRP AS 100192.168.1.96 /30 10.20.20.0 /24 EIGRP Update: Connected to 10.0.0.0 /8R2(config)# router eigrp 100R2(config)# no auto-summaryR2(config)# endR2# show ip route<output omitted>Gateway of last resort is 192.168.1.2 to network 0.0.0.010.0.0.0/24 is subnetted, 2 subnetsC 10.20.20.0 is directly connected, FastEthernet0/0D 10.10.10.0 [90/40514560] via 192.168.1.101, 00:05:21, Serial0/0/0192.168.1.0/27 is subnetted, 2 subnetsC 192.168.1.96 is directly connected, Serial0/0/0C 192.168.1.0 is directly connected, Serial0/0/1S* 0.0.0.0/0 [1/0] via 192.168.1.2R2#
  • Chapter 2103© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicSummarizing on an Interface Earlier distance vector protocols were unable to createsummary routes other than the classful boundaries or /8,/16/ or /24. To address this shortcoming, EIGRP added the ipsummary-address eigrp interface configurationcommand.• The command is used to create one or more summary routes within anetwork on any bit boundary (as long as a more specific route existsin the routing table). IP EIGRP summary routes are given an administrativedistance value of 5.• Standard EIGRP routes receive an administrative distance of 90• External EIGRP routes receive an administrative distance of 170.
  • Chapter 2104© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Publicip summary-address eigrp Manually create a summary route at an arbitrary bit boundary.Router(config-if)#ip summary-address eigrp as-number address mask [admin-distance]Parameter Descriptionas-number The number of the EIGRP AS is identified.addressThe IP address being advertised as the summaryaddress. This address does not need to be alignedon Class A, B, or C boundaries.mask The IP subnet mask used to create the summaryaddress.admin-distance (Optional) Administrative distance. A value from 0 to255.
  • Chapter 2105© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Route SummarizationR1(config)# router eigrp 100R1(config)# no auto-summaryR2(config)# router eigrp 100R2(config)# no auto-summaryFa0/0Fa0/0R1 R210.10.10.0 /24EIGRP AS 100WAN192.168.3.1S0/0/010.10.20.0 /2410.0.0.0 /8R3R3(config)# interface S0/0/0R3(config-if)# ip address 192.168.3.1 255.255.255.0R3(config-if)# ip summary-address eigrp 1 10.10.0.0 255.255.0.0R3(config-if)# no shutR3(config-if)# exitR3# show ip protocolsRouting Protocol is "eigrp 100"<output omitted>Automatic network summarization is not in effectAddress Summarization:10.10.0.0/16 for Serial0/0/0<output omitted>
  • Chapter 2106© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicConfiguring andVerifying EIGRPin an EnterpriseWAN
  • Chapter 2107© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP and WAN Considerations There are various deployment options available forsupporting EIGRP over a WAN including:• Frame Relay• Frame-Relay using dynamic mapping• Frame-Relay using static mapping• Multipoint and point-to-point Frame-Relay subinterfaces• Multiprotocol Label Switching (MPLS) virtual private networks (VPNs),• Ethernet over Multiprotocol Label Switching (EoMPLS) Other considerations include:• EIGRP load balancing• Limiting EIGRP bandwidth utilization on WAN links
  • Chapter 2108© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicFrame Relay Using Dynamic Mapping Easy deployment due to the use of inverse ARP. Auto detects most settings. Inverse-ARP will dynamically map the IP addresses of thedevices at the other ends of the PVCs to the local DLCInumber. Consists of three steps:1. Configure an IP address on the serial interface.2. Change the encapsulation on an interface using theencapsulation frame-relay command.3. Activate the interface.
  • Chapter 2109© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicFrame Relay Using Dynamic MappingR1(config)# interface S0/0/0R1(config-if)# encapsulation frame-relayR1(config-if)# ip address 192.168.1.101 255.255.255.0R1(config-if)# exitR1(config)# router eigrp 100R1(config-router)# network 172.16.1.0 0.0.0.255R1(config-router)# network 192.168.1.0R1(config-router)#R3(config)# interface S0/0/0R3(config-if)# encapsulation frame-relayR3(config-if)# ip address 192.168.1.103 255.255.255.0R3(config-if)# exitR3(config)# router eigrp 100R3(config-router)# network 172.16.3.0 0.0.0.255R3(config-router)# network 192.168.1.0R3(config-router)#Fa0/0R1172.16.1.0 /24EIGRP AS 100Frame RelayR2R3S0/0/0192.168.1.0 /24.101.103.102S0/0/0S0/0/0DLCI 103DLCI 102 DLCI 201DLCI 301Fa0/0172.16.2.0 /24Fa0/0172.16.3.0 /24
  • Chapter 2110© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicFrame Relay Using Dynamic MappingR1# show ip eigrp neighborsIP-EIGRP neighbors for process 100H Address Interface Hold Uptime SRTT RTO Q Seq(sec) (ms) Cnt Num0 192.168.1.102 Se0/0/0 10 00:07:22 10 2280 0 51 192.168.1.103 Se0/0/0 10 00:09:34 10 2320 0 9R1#R3# show ip eigrp neighborsIP-EIGRP neighbors for process 100H Address Interface Hold Uptime SRTT RTO Q Seq(sec) (ms) Cnt Num0 192.168.1.101 Se0/0/0 10 00:11:45 10 1910 0 6R3#Fa0/0R1172.16.1.0 /24EIGRP AS 100Frame RelayR2R3S0/0/0192.168.1.0 /24.101.103.102S0/0/0S0/0/0DLCI 103DLCI 102 DLCI 201DLCI 301Fa0/0172.16.2.0 /24Fa0/0172.16.3.0 /24
  • Chapter 2111© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicFrame Relay Using Static Mapping Deploying static maps automatically disables the inverse-ARP feature. Consists of four steps:1. Configure an IP address on the serial interface.2. Change the encapsulation on an interface using theencapsulation frame-relay command.3. Map the IP-to-DLCI mapping commands on the interface using theframe-relay map command.4. Activate the interface.
  • Chapter 2112© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Publicframe-relay map Command Statically map the remote routers IP address to the localDLCI.Router(config-if)#frame-relay map protocol protocol-address dlci [broadcast] [ietf |cisco] [payload-compress {packet-by-packet | frf9 stack}]Parameter Descriptionprotocol Defines the supported protocol, bridging, or logical link control.protocol-address Defines the network layer address of the destination router interface.dlci Defines the local DLCI that is used to connect to the remote protocol address.broadcast (Optional) Allows broadcasts and multicasts over the VC, permitting the use ofdynamic routing protocols over the VC.ietf | cisco Enables IETF or Cisco encapsulations.payload-compress (Optional) Enables payload compression.packet-by-packet (Optional) Enables packet-by-packet payload compression, using the Stackermethod, a Cisco proprietary compression method.frf9 stac (Optional) Enables FRF.9 compression using the Stacker method.
  • Chapter 2113© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicFrame Relay Using Static MappingR1(config)# interface S0/0/0R1(config-if)# encapsulation frame-relayR1(config-if)# ip address 192.168.1.101 255.255.255.0R1(config-if)# frame-relay map ip 192.168.1.101 101R1(config-if)# frame-relay map ip 192.168.1.102 102 broadcastR1(config-if)# frame-relay map ip 192.168.1.103 103 broadcastR1(config-if)#R3(config)# interface S0/0/0R3(config-if)# encapsulation frame-relayR3(config-if)# ip address 192.168.1.103 255.255.255.0R3(config-if)# frame-relay map ip 192.168.1.101 301R3(config-if)# frame-relay map ip 192.168.1.102 301 broadcastR3(config-if)# frame-relay map ip 192.168.1.103 301 broadcastR3(config-if)#Fa0/0R1172.16.1.0 /24EIGRP AS 100Frame RelayR2R3S0/0/0192.168.1.0 /24.101.103.102S0/0/0S0/0/0DLCI 103DLCI 102 DLCI 201DLCI 301Fa0/0172.16.2.0 /24Fa0/0172.16.3.0 /24
  • Chapter 2114© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicFrame Relay Using Static MappingR1# show ip eigrp neighborsIP-EIGRP neighbors for process 100H Address Interface Hold Uptime SRTT RTO Q Seq(sec) (ms) Cnt Num0 192.168.1.102 Se0/0/0 10 00:06:20 10 2280 0 51 192.168.1.103 Se0/0/0 10 00:08:31 10 2320 0 9R3# show ip eigrp neighborsIP-EIGRP neighbors for process 100H Address Interface Hold Uptime SRTT RTO Q Seq(sec) (ms) Cnt Num0 192.168.1.101 Se0/0/0 10 00:10:44 10 1910 0 61 192.168.1.102 Se0/0/0 10 00:03:02 10 2210 0 3Fa0/0R1172.16.1.0 /24EIGRP AS 100Frame RelayR2R3S0/0/0192.168.1.0 /24.101.103.102S0/0/0S0/0/0DLCI 103DLCI 102 DLCI 201DLCI 301Fa0/0172.16.2.0 /24Fa0/0172.16.3.0 /24
  • Chapter 2115© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP over FR Multipoint Subinterfaces Multipoint subinterfaces can be created using a singleFrame Relay physical interface.• Uses a single subnet, preserving the IP address space. Frame Relay multipoint is applicable to partial mesh and fullmesh topologies. Consists of several steps:• Configure the physical interface with no IP address and change theencapsulation to Frame Relay.• Create a serial multipoint subinterface.• Configure an IP address on the serial interface.• Map the IP-to-DLCI mapping commands on the interface using theframe-relay map command.• Either rely on dynamic mapping or configure a local DLCI value usingthe frame-relay interface-dlci command.
  • Chapter 2116© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP over FR Multipoint Subinterfaces Multipoint subinterfaces are configured with theinterface serial number.subinterface-numbermultipoint command. The IP address-to-DLCI mapping is done by either:• Specifying the local DLCI value (using the frame-relayinterface-dlci dlci command) and relying on Inverse ARP• Using manual IP address-to-DLCI mapping.
  • Chapter 2117© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP over FR Multipoint SubinterfacesFa0/0R1172.16.1.0 /24EIGRP AS 100Frame RelayR2R3192.168.1.0 /24.103.102S0/0/0.1S0/0/0.1DLCI 103DLCI 102 DLCI 201DLCI 301Fa0/0172.16.2.0 /24Fa0/0172.16.3.0 /24S0/0/0.1.101R1(config)# interface S0/0/0R1(config-if)# no ip addressR1(config-if)# encapsulation frame-relayR1(config-if)# exitR1(config)# interface Serial0/0/0.1 multipointR1(config-subif)# ip address 192.168.1.101 255.255.255.0R1(config-subif)# no ip split-horizon eigrp 100R1(config-subif)# frame-relay map ip 192.168.1.101 101R1(config-subif)# frame-relay map ip 192.168.1.102 102 broadcastR1(config-subif)# frame-relay map ip 192.168.1.103 103 broadcastR1(config-subif)#
  • Chapter 2118© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP over FR Multipoint SubinterfacesR1# show ip eigrp neighborsIP-EIGRP neighbors for process 100H Address Interface Hold Uptime SRTT RTO Q Seq(sec) (ms) Cnt Num0 192.168.1.102 Se0/0/0.1 10 00:06:41 10 2280 0 51 192.168.1.103 Se0/0/0.1 10 00:08:52 10 2320 0 9R3# show ip eigrp neighborsIP-EIGRP neighbors for process 100H Address Interface Hold Uptime SRTT RTO Q Seq(sec) (ms) Cnt Num0 192.168.1.101 Se0/0/0.1 10 00:10:37 10 1910 0 61 192.168.1.102 Se0/0/0.1 10 00:03:12 10 2210 0 3Fa0/0R1172.16.1.0 /24EIGRP AS 100Frame RelayR2R3192.168.1.0 /24.103.102S0/0/0.1S0/0/0.1DLCI 103DLCI 102 DLCI 201DLCI 301Fa0/0172.16.2.0 /24Fa0/0172.16.3.0 /24S0/0/0.1.101
  • Chapter 2119© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Unicast Neighbors Define a neighboring router to exchange EIGRP routing information.Router(config-router)#neighbor {ip-address | ipv6-address} interface-typeinterface-number EIGRP exchanges routing information with the specified neighborusing unicast packets. Multiple neighbor statements can be used to establish peeringsessions with multiple specific EIGRP neighbors. The interface through which EIGRP will exchange routing updatesmust be specified in the neighbor statement. The interfaces through which two EIGRP neighbors exchange routingupdates must be configured with IP addresses from the samenetwork.
  • Chapter 2120© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Unicast NeighborsFa0/0R1172.16.1.0 /24EIGRP AS 100Frame RelayR2R3192.168.1.0 /24.103.102S0/0/0.1S0/0/0.1DLCI 103DLCI 102 DLCI 201DLCI 301Fa0/0172.16.2.0 /24Fa0/0172.16.3.0 /24S0/0/0.1.101R1(config)# interface S0/0/0R1(config-if)# no ip addressR1(config-if)# encapsulation frame-relayR1(config-if)# interface S0/0/0.1 multipointR1(config-subif)# ip address 192.168.1.101 255.255.255.0R1(config-subif)# frame-relay map ip 192.168.1.102 102 broadcastR1(config-subif)# frame-relay map ip 192.168.1.103 103 broadcastR1(config-subif)# router eigrp 100R1(config-router)# neighbor 192.168.1.102 S0/0/0.1R1(config-router)#
  • Chapter 2121© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Unicast NeighborsFa0/0R1172.16.1.0 /24EIGRP AS 100Frame RelayR2R3192.168.1.0 /24.103.102S0/0/0.1S0/0/0.1DLCI 103DLCI 102 DLCI 201DLCI 301Fa0/0172.16.2.0 /24Fa0/0172.16.3.0 /24S0/0/0.1.101R2(config)# interface S0/0/0R2(config-if)# no ip addressR2(config-if)# encapsulation frame-relayR2(config-if)# interface S0/0/0.1 multipointR2(config-subif)# ip address 192.168.1.102 255.255.255.0R2(config-subif)# frame-relay map ip 192.168.1.101 201 broadcastR2(config-subif)# router eigrp 100R2(config-router)# neighbor 192.168.1.101 S0/0/0.1R2(config-router)#
  • Chapter 2122© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP over FR Point-to-Point Subinterfaces Point-to-point subinterfaces can be created using a singleFrame Relay physical interface.• Uses multiple subnets. Frame Relay point-to point is applicable to hub and spoketopologies. Consists of several steps:• Configure the physical interface with no IP address and change theencapsulation to Frame Relay.• Create a serial point-to-point subinterface.• Configure an IP address on the serial interface.• Configure a local DLCI value using the frame-relay interface-dlci command.
  • Chapter 2123© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP over FR Point-to-Point Subinterfaces Multipoint subinterfaces are configured with theinterface serial number.subinterface-numbermultipoint command. The IP address-to-DLCI mapping is done by either:• Specifying the local DLCI value (using the frame-relayinterface-dlci dlci command) and relying on Inverse ARP.
  • Chapter 2124© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP over FR Point-to-Point SubinterfacesR1(config)# interface S0/0/0R1(config-if)# no ip addressR1(config-if)# encapsulation frame-relayR1(config-if)# exitR1(config)# interface Serial0/0/0.2 point-to-pointR1(config-subif)# ip address 192.168.2.101 255.255.255.0R1(config-subif)# frame-relay interface-dlci 102R1(config-subif)#R1(config-subif)# interface Serial0/0/0.3 point-to-pointR1(config-subif)# ip address 192.168.3.101 255.255.255.0R1(config-subif)# frame-relay interface-dlci 103R1(config-subif)#Fa0/0R1172.16.1.0 /24EIGRP AS 100Frame RelayR2R3192.168.3.103S0/0/0.1S0/0/0.1DLCI 103DLCI 102 DLCI 201DLCI 301Fa0/0172.16.2.0 /24Fa0/0172.16.3.0 /24S0/0/0.3=192.168.3.101/24192.168.2.102S0/0/0.2=192.168.2.101/24
  • Chapter 2125© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP over FR Point-to-Point SubinterfacesR1# show ip eigrp neighborsIP-EIGRP neighbors for process 100H Address Interface Hold Uptime SRTT RTO Q Seq(sec) (ms) Cnt Num0 192.168.2.102 Se0/0/0.2 10 00:08:04 10 2280 0 51 192.168.3.103 Se0/0/0.3 10 00:10:12 10 2320 0 9R3# show ip eigrp neighborsIP-EIGRP neighbors for process 100H Address Interface Hold Uptime SRTT RTO Q Seq(sec) (ms) Cnt Num0 192.168.3.101 Se0/0/0.1 10 00:13:25 10 1910 0 6Fa0/0R1172.16.1.0 /24EIGRP AS 100Frame RelayR2R3192.168.3.103S0/0/0.1S0/0/0.1DLCI 103DLCI 102 DLCI 201DLCI 301Fa0/0172.16.2.0 /24Fa0/0172.16.3.0 /24S0/0/0.3=192.168.3.101/24192.168.2.102S0/0/0.2=192.168.2.101/24
  • Chapter 2126© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP over MPLS Multi-Protocol Label Switching (MPLS) is an InternetEngineering Task Force (IETF) standard architecture thatcombines the advantages of Layer 3 routing with thebenefits of Layer 2 switching. A unique feature of MPLS is its capability to perform labelstacking, in which multiple labels can be carried in a packet. The top label, which is the last one in, is always processedfirst.• Label stacking enables multiple LSPs to be aggregated, therebycreating tunnels through multiple levels of an MPLS network.
  • Chapter 2127© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP over Layer 3 MPLS VPNsR1(config)# interface FastEthernet0/0R1(config-if)# ip address 192.168.1.2 255.255.255.252R1(config-if)# exitR1(config)# router eigrp 100R1(config-router)# network 172.16.1.0 0.0.0.255R1(config-router)# network 192.168.1.0R1(config-router)#R2(config)# interface FastEthernet0/0R2(config-if)# ip address 192.168.2.2 255.255.255.252R2(config-if)# exitR2(config)# router eigrp 100R2(config-router)# network 172.17.2.0 0.0.0.255R2(config-router)# network 192.168.2.0R2(config-router)#EIGRP AS 100Layer 3 MPLSVPN BackboneFa0/0 PE1.1PE2192.168.2.0/30.2.2192.168.1.0/30.1EIGRP AS 100Fa0/0172.16.1.0 /24 172.17.2.0 /24R2R1
  • Chapter 2128© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP over Layer 3 MPLS VPNsR1# show ip eigrp neighborsIP-EIGRP neighbors for process 100H Address Interface Hold Uptime SRTT RTO Q Seq(sec) (ms) Cnt Num0 192.168.1.1 Fe0/0 10 00:07:22 10 2280 0 5R2# show ip eigrp neighborsIP-EIGRP neighbors for process 100H Address Interface Hold Uptime SRTT RTO Q Seq(sec) (ms) Cnt Num0 192.168.2.1 Fe0/0 10 00:17:02 10 1380 0 5EIGRP AS 100Layer 3 MPLSVPN BackboneFa0/0 PE1.1PE2192.168.2.0/30.2.2192.168.1.0/30.1EIGRP AS 100Fa0/0172.16.1.0 /24 172.17.2.0 /24R2R1
  • Chapter 2129© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP over Layer 2 MPLS VPNsR1(config)# interface FastEthernet0/0R1(config-if)# ip address 192.168.1.101 255.255.255.224R1(config-if)# exitR1(config)# router eigrp 100R1(config-router)# network 172.16.1.0 0.0.0.255R1(config-router)# network 192.168.1.0R1(config-router)#R2(config)# interface FastEthernet0/0R2(config-if)# ip address 192.168.1.102 255.255.255.224R2(config-if)# exitR2(config)# router eigrp 100R2(config-router)# network 172.17.2.0 0.0.0.255R2(config-router)# network 192.168.1.0R2(config-router)#EIGRP AS 100Layer 2 MPLSVPN BackboneFa0/0 PE1 PE2192.168.1.0/27.102.101192.168.1.0/27EIGRP AS 100Fa0/0172.16.1.0 /24 172.17.2.0 /24R2R1
  • Chapter 2130© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP over Layer 2 MPLS VPNsR1# show ip eigrp neighborsIP-EIGRP neighbors for process 100H Address Interface Hold Uptime SRTT RTO Q Seq(sec) (ms) Cnt Num0 192.168.1.102 Fe0/0 10 00:07:22 10 2280 0 5R2# show ip eigrp neighborsIP-EIGRP neighbors for process 100H Address Interface Hold Uptime SRTT RTO Q Seq(sec) (ms) Cnt Num0 192.168.1.101 Fe0/0 10 00:17:02 10 1380 0 5EIGRP AS 100Layer 2 MPLSVPN BackboneFa0/0 PE1 PE2192.168.1.0/27.102.101192.168.1.0/27EIGRP AS 100Fa0/0172.16.1.0 /24 172.17.2.0 /24R2R1
  • Chapter 2131© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Load Balancing Routes with a metric equal to the minimum metric areinstalled in the routing table.• Referred to as ―equal-cost load balancing‖.• All IP routing protocols on Cisco routers can perform equal-cost loadbalancing. The maximum-paths maximum-path command can beused to allow up to 6 equal-cost paths.• Default is 4.• Setting the maximum-path option to 1 disables load balancing.
  • Chapter 2132© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Equal-Cost Load BalancingR1(config)# router eigrp 100R1(config-router)# network 172.16.1.0 0.0.0.255R1(config-router)# network 192.168.1.0R1(config-router)# network 192.168.2.0R1(config-router)# network 192.168.3.0R1(config-router)# network 192.168.4.0R1(config-router)# maximum–paths 3R1(config-router)#R1 Topology TableAdvertised Distance (AD)Network Neighbor AD FD172.16.2.0/24 R2 20 40R3 20 40R4 20 40R5 20 40
  • Chapter 2133© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicUnequal Cost Load Balancing EIGRP can also balance traffic across multiple routes thathave different metrics.• Referred to as unequal-cost load balancing. The degree to which EIGRP performs load balancing iscontrolled with the variance multiplier command.• The multiplier is a value, between 1 and 128, used for load balancing.• The default is 1, which means equal-cost load balancing.• Setting a variance value greater than 1 allows EIGRP to installmultiple loop-free routes with unequal cost in the routing table.• EIGRP will always install successors (the best routes) in the routingtable.• The variance allows feasible successors (and only feasible successorroutes) as candidate routes to potentially be installed in the routing table.
  • Chapter 2134© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Unequal-Cost Load BalancingR1(config)# router eigrp 100R1(config-router)# variance 2R1(config-router)#R1 Topology TableAdvertised Distance (AD)Network Neighbor AD FD172.16.2.0/24 R2 10 30R3 10 20R4 25 45R5 10 50
  • Chapter 2135© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Bandwidth Use Across WAN Links EIGRP operates efficiently in WAN environments and isscalable on both point-to-point links and NBMA multipointand point-to-point links. However, default configuration of WAN connections maynot be optimal therefore a solid understanding of EIGRPoperation coupled with knowledge of link speeds can yieldan efficient, reliable, scalable router configuration. There are two commands which could be configured toimprove EIGRP operation:• bandwidth• ip percent-bandwidth
  • Chapter 2136© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicSetting EIGRP Bandwidth on a WAN EIGRP assumes the default bandwidth on the link instead of thetrue bandwidth, therefore suboptimal path selection may result.• For example, Serial links commonly default to 1.5 Mbps however theactual CIR may be 128 Kbps.• DUAL would use the 1.5 Mbps value instead of the actual slower 128Kbps value in its metric calculation. It is recommended to configure the bandwidth setting using thebandwidth kilobits on serial interfaces. An important WAN consideration is the fact that multipointinterfaces physical bandwidth setting is shared equally by allneighbors.• EIGRP uses the bandwidth setting of the physical interface divided bythe number of Frame Relay neighbors connected on that physicalinterface to get the bandwidth attributed to each neighbor.• The EIGRP configuration should reflect the correct percentage of theactual available bandwidth on the line.
  • Chapter 2137© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP WAN Configuration – Example #1 All VCs share the bandwidth evenly:4 (VC) x 56 (CIR) = 224CIR 56R1EIGRP AS 100Frame RelayR3R4R2R5CIR 56CIR 56CIR 56T1 (1.5 Mbps)S0/0/0R1(config)# interface S0/0/0R1(config-if)# encapsulation frame-relayR1(config-if)# bandwidth 224
  • Chapter 2138© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP WAN Configuration – Example #2a R2, R3, and R4 share the same CIR. To protect against overwhelmingthe slowest-speed circuit (to R5) the bandwidth should be configured tothe lowest CIR multiplied by the number of circuits.4 (VC) x 56 (CIR) = 224R1(config)# interface S0/0/0R1(config-if)# encapsulation frame-relayR1(config-if)# bandwidth 224R1EIGRP AS 100Frame RelayR3R4R2R5T1 (1.5 Mbps)S0/0/0CIR 256BW 224 CIR 256BW 224CIR 256BW 224CIR 56BW 56
  • Chapter 2139© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP WAN Configuration – Example #2b An alternate solution is to configure a multipoint subinterface for routers R2, R3, andR4 and configure a point-to-point subinterface network for R5.R1EIGRP AS 100Frame RelayR3R4R2R5T1 (1.5 Mbps)S0/0/0CIR 256BW 224 CIR 256BW 224CIR 256BW 224CIR 56BW 56R1(config)# interface S0/0/0R1(config-if)# encapsulation frame-relayR1(config-if)# interface S0/0/0/0.1 multipointR1(config-subif)# bandwidth 768R1(config-subif)# exitR1(config)# interface S0/0/0/0.2 point-to-pointR1(config-subif)# bandwidth 56R1(config-subif)#
  • Chapter 2140© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP ip bandwith-percent By default, EIGRP is set to use up to 50% of the bandwidthof an interface to exchange routing information. The ip bandwidth-percent eigrp command can beconfigured to control the amount of bandwidth available toEIGRP.• This is not the same as the bandwidth command.• However, this command relies on the value set by the bandwidthcommand.
  • Chapter 2141© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Publicip bandwidth-percent eigrp Configure the amount of bandwidth available to EIGRP.Router(config-if)#ip bandwidth-percent eigrp as-number percent The as-number is the EIGRP AS number. The percent parameter is the percentage of theconfigured bandwidth that EIGRP can use. The percentage value can be set to greater than 100.
  • Chapter 2142© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicConfiguring andVerifying EIGRPAuthentication
  • Chapter 2143© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicRouter Authentication Many routing protocols support authentication such that arouter authenticates the source of each routing updatepacket that it receives. Simple password authentication is supported by:• IS-IS• OSPF• RIPv2 MD5 authentication is supported by:• OSPF• RIPv2• BGP• EIGRP
  • Chapter 2144© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicSimple Password vs. MD5 Authentication Simple password authentication:• Router sends packet and key.• Neighbor checks if received key matches its key.• Is not secure. MD5 authentication:• Configure a ―key‖ (password) and key-id; router generates a messagedigest, or hash, of the key, key-id and message.• Message digest is sent with packet; key is not sent.• Is secure.
  • Chapter 2145© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP MD5 Authentication EIGRP supports MD5 authentication. Router generates and checks every EIGRP packet. Routerauthenticates the source of each routing update packet thatit receives. Configure a ―key‖ (password) and key-id; each participatingneighbor must have same key configured.
  • Chapter 2146© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicMD5 Authentication EIGRP MD5 authentication:• Router generates a message digest, or hash, of the key, key-id, andmessage.• EIGRP allows keys to be managed using key chains.• Specify key-id (number, key, and lifetime of key).• First valid activated key, in order of key numbers, is used.
  • Chapter 2147© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicPlanning for EIGRP The following key parameters must be defined in enoughdetail before configuring EIGRP authentication:• The EIGRP AS number• The authentication mode (MD5)• The definition of one or more keys to authenticate EIGRP packets,according to the network security plan.• The keys’ lifetime, if multiple keys are defined. Once defined, the following steps may be implemented:1. Configure the authentication mode for EIGRP.2. Configure the key chain.3. Optionally configure the keys’ lifetime parameters.4. Enable authentication to use the key(s) in the key chain.
  • Chapter 2148© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicConfigure the Authentication Mode for EIGRP Specify MD5 authentication for EIGRP packets.Router(config-if)#ip authentication mode eigrp autonomous-system md5 Enable EIGRP packet authentication using key in the key-chain.Router(config-if)#ip authentication key-chain eigrp autonomous-system name-of-chain
  • Chapter 2149© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicConfigure the Key Chain Define the keychain in key chain configuration mode.Router(config)#key chain name-of-chain Identify the key and enter the key-id configuration mode.Router(config-keychain)#key key-idRouter(config-keychain-key)#key-string text Identify key string (password)
  • Chapter 2150© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicConfigure Keys Lifetime Parameters (Optional) Specify when the key will be accepted for received packets.Router(config-keychain-key)#accept-lifetime start-time {infinite | end-time |duration seconds} Specify when the key can be used for sending EIGRP packets.Router(config-keychain-key)#send-lifetime start-time {infinite | end-time |duration seconds}
  • Chapter 2151© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEnable Authentication to Use the Key Chain Enable EIGRP packet authentication using key in the key-chain.Router(config-if)#ip authentication key-chain eigrp autonomous-systemname-of-chain
  • Chapter 2152© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicConfiguring EIGRP MD5 AuthenticationFa0/0Fa0/0R1 R2172.16.1.0 /24EIGRP AS 100R1# show running-config!<output omitted>!key chain R1chainkey 1key-string FIRST-KEYaccept-lifetime 04:00:00 Jan 1 2009 infinitesend-lifetime 04:00:00 Jan 1 2009 04:00:00 Jan 31 2009key 2key-string SECOND-KEYaccept-lifetime 04:00:00 Jan 25 2009 infinitesend-lifetime 04:00:00 Jan 25 2009 infinite!<output omitted>!interface FastEthernet0/0ip address 172.16.1.1 255.255.255.0!interface Serial0/0/0bandwidth 64ip address 192.168.1.101 255.255.255.224ip authentication mode eigrp 100 md5ip authentication key-chain eigrp 100 R1chain!router eigrp 100network 172.16.1.0 0.0.0.255network 192.168.1.0auto-summary172.17.2.0 /24S0/0/0S0/0/064 kbps192.168.1.96 /27.101.102.1.1
  • Chapter 2153© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicConfiguring EIGRP MD5 AuthenticationFa0/0Fa0/0R1 R2172.16.1.0 /24EIGRP AS 100 R2# show running-config!<output omitted>!key chain R2chainkey 1key-string FIRST-KEYaccept-lifetime 04:00:00 Jan 1 2009 infinitesend-lifetime 04:00:00 Jan 1 2009 infinitekey 2key-string SECOND-KEYaccept-lifetime 04:00:00 Jan 25 2009 infinitesend-lifetime 04:00:00 Jan 25 2009 infinite!<output omitted>!interface FastEthernet0/0ip address 172.17.2.2 255.255.255.0!interface Serial0/0/0bandwidth 64ip address 192.168.1.102 255.255.255.224ip authentication mode eigrp 100 md5ip authentication key-chain eigrp 100 R2chain!router eigrp 100network 172.17.2.0 0.0.0.255network 192.168.1.0auto-summary172.17.2.0 /24S0/0/0S0/0/064 kbps192.168.1.96 /27.101.102.1.1
  • Chapter 2154© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicVerifying MD5 AuthenticationR1#*Apr 21 16:23:30.517: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 192.168.1.102(Serial0/0/0) is up: new adjacencyR1#R1# show ip eigrp neighborsIP-EIGRP neighbors for process 100H Address Interface Hold Uptime SRTT RTO Q Seq(sec) (ms) Cnt Num0 192.168.1.102 Se0/0/0 12 00:03:10 17 2280 0 14R1#R1# show ip route<output omitted>Gateway of last resort is not setD 172.17.0.0/16 [90/40514560] via 192.168.1.102, 00:02:22, Serial0/0/0172.16.0.0/16 is variably subnetted, 2 subnets, 2 masksD 172.16.0.0/16 is a summary, 00:31:31, Null0C 172.16.1.0/24 is directly connected, FastEthernet0/0192.168.1.0/24 is variably subnetted, 2 subnets, 2 masksC 192.168.1.96/27 is directly connected, Serial0/0/0D 192.168.1.0/24 is a summary, 00:31:31, Null0R1#R1# ping 172.17.2.2Type escape sequence to abort.Sending 5, 100-byte ICMP Echos to 172.17.2.2, timeout is 2 seconds:!!!!!Success rate is 100 percent (5/5), round-trip min/avg/max = 12/15/16 ms
  • Chapter 2155© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicVerifying MD5 AuthenticationR1# show key chainKey-chain R1chain:key 1 -- text “FIRST-KEY"accept lifetime (04:00:00 Jan 1 2009) - (always valid) [valid now]send lifetime (04:00:00 Jan 1 2009) - (04:00:00 Jan 31 2009)key 2 -- text “SECOND-KEY"accept lifetime (04:00:00 Jan 25 2009) - (always valid) [valid now]send lifetime (04:00:00 Jan 25 2009) - (always valid) [valid now]
  • Chapter 2156© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicTroubleshooting MD5 AuthenticationR1# debug eigrp packetsEIGRP Packets debugging is on(UPDATE, REQUEST, QUERY, REPLY, HELLO, IPXSAP, PROBE, ACK, STUB, SIAQUERY, SIAREPLY)*Jan 21 16:38:51.745: EIGRP: received packet with MD5 authentication, key id = 1*Jan 21 16:38:51.745: EIGRP: Received HELLO on Serial0/0/0 nbr 192.168.1.102*Jan 21 16:38:51.745: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely0/0R2# debug eigrp packetsEIGRP Packets debugging is on(UPDATE, REQUEST, QUERY, REPLY, HELLO, IPXSAP, PROBE, ACK, STUB, SIAQUERY, SIAREPLY)R2#*Jan 21 16:38:38.321: EIGRP: received packet with MD5 authentication, key id = 2*Jan 21 16:38:38.321: EIGRP: Received HELLO on Serial0/0/0 nbr 192.168.1.101*Jan 21 16:38:38.321: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely0/0
  • Chapter 2157© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicConfiguring EIGRP MD5 AuthenticationFa0/0Fa0/0R1 R2172.16.1.0 /24EIGRP AS 100R1(config-if)# key chain R1chainR1(config-keychain)# key 2R1(config-keychain-key)# key-string wrongkeyR1(config-keychain-key)#172.17.2.0 /24S0/0/0S0/0/064 kbps192.168.1.96 /27.101.102.1.1R2# debug eigrp packetsEIGRP Packets debugging is on(UPDATE, REQUEST, QUERY, REPLY, HELLO, IPXSAP, PROBE, ACK, STUB, SIAQUERY, SIAREPLY)*Jan 21 16:50:18.749: EIGRP: pkt key id = 2, authentication mismatch*Jan 21 16:50:18.749: EIGRP: Serial0/0/0: ignored packet from 192.168.1.101, opcode = 5 (invalidauthentication)*Jan 21 16:50:18.749: EIGRP: Dropping peer, invalid authentication*Jan 21 16:50:18.749: EIGRP: Sending HELLO on Serial0/0/0*Jan 21 16:50:18.749: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0*Jan 21 16:50:18.753: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 192.168.1.101(Serial0/0/0) is down: Auth failureR2#R2# show ip eigrp neighborsIP-EIGRP neighbors for process 100R2#
  • Chapter 2158© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicOptimizing EIGRPImplementations
  • Chapter 2159© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicFactors That Influence EIGRP Scalability Quantity of routing information exchanged between peers:without proper route summarization, this can be excessive. Number of routers that must be involved when a topologychange occurs. Depth of topology: the number of hops that information musttravel to reach all routers. Number of alternate paths through the network.
  • Chapter 2160© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Query Process Queries are sent when a route is lost and no feasiblesuccessor is available. The lost route is now in ―active‖ state. Queries are sent to all neighboring routers on all interfacesexcept the interface to the successor. If the neighbors do not have their lost-route information,queries are sent to their neighbors. If a router has an alternate route, it answers the query; thisstops the query from spreading in that branch of thenetwork.
  • Chapter 2161© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicOverwhelming EIGRP Query Process In a large internetwork EIGRP queries can generate manyresources. Several solutions exist to optimize the query propagation processand to limit the amount of unnecessary EIGRP load on the links,including:• Summarization• Redistribution• EIGRP stub routing feature.
  • Chapter 2162© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicStuck-in-Active If a router does not receive a reply to all the outstandingqueries within default 3 minutes (180 seconds), the routegoes into Stuck-in-Active (SIA) state. Common SIA reasons:• A router is too busy to answer the query.• A router cannot allocate the memory to process the query.• The circuit between the two routers is not reliable.• The router has unidirectional links. SIA solutions:• Redesign the network to limit the query range by route summarizationand the ip summary-address eigrp command.• Configure the remote routers as stub EIGRP routers.
  • Chapter 2163© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicSIA Solution: Summarization Poorly designed networks can make summarization difficult. Manually summarize the routes whenever possible to support a hierarchicalnetwork design. The more networks EIGRP summarizes, the lower the number of queriesbeing sent out.• Ultimately reduces the occurrence of SIA errors.
  • Chapter 2164© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicSIA Solution: Summarization This network design is better because subnet addresses from individualmajor networks are localized within each cloud, allowing summary routesconfigured using the ip summary-address eigrp command to beinjected into the core. As an added benefit, the summary routes act as a boundary for the queriesgenerated by a topology change.
  • Chapter 2165© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicSIA Solution: Stub Networks The EIGRP Stub Routing feature:• Improves network stability• Reduces resource utilization and• Simplifies remote router (spoke) configuration
  • Chapter 2166© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Stub Routing Stub routing is commonly used in hub-and-spoke topology. Stub router sends a special peer information packet to allneighboring routers to report its status as a stub router.• Any neighbor that receives a packet informing it of the stub statusdoes not query the stub router for any routes.• Stub routers are not queried and instead, hub routers connected tothe stub router answer the query on behalf of the stub router. Only the remote routers are configured as stubs.
  • Chapter 2167© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicEIGRP Stub Configure a router as a stub router.Router(config-router)#eigrp stub [receive-only | connected | static | summary | redistributed]Parameter Descriptionreceive-onlyRestricts the router from sharing any of its routes with any other router withinan EIGRP AS.Keyword cannot be combined with any other keyword.connectedPermits the EIGRP stub routing feature to send connected routes.This option is enabled by default and is the most widely practical stub option.staticPermits the EIGRP stub routing feature to send static routes.Redistributing static routes with the redistribute static command is stillnecessary.summaryPermits the EIGRP stub routing feature to send automatically summarized and/ or manually summarized routes.This option is enabled by default.redistributedPermits the EIGRP stub routing feature to send redistributed routes.Redistributing routes with the redistribute command is still necessary.
  • Chapter 2168© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicExample: EIGRP Stub Parameters If stub connected isconfigured:• B will advertise 10.1.2.0/24 to A.• B will not advertise 10.1.2.0/23,10.1.3.0/23, or 10.1.4.0/24. If stub summary isconfigured:• B will advertise 10.1.2.0/23 to A.• B will not advertise 10.1.2.0/24,10.1.3.0/24, or 10.1.4.0/24.
  • Chapter 2169© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicExample: EIGRP Stub Parameters (Cont.) If stub static isconfigured:• B will advertise 10.1.4.0/24 to A.• B will not advertise 10.1.2.0/24,10.1.2.0/23, or 10.1.3.0/24. If stub receive-only isconfigured:• B won’t advertise anything to A,so A needs to have a staticroute to the networks behind Bto reach them.
  • Chapter 2170© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicGraceful Shutdown
  • Chapter 2171© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicChapter 2 SummaryThe chapter focused on the following topics: Features of EIGRP, including fast convergence, use of partial updates, multiple network layer support,use of multicast and unicast, VLSM support, seamless connectivity across all data link layer protocolsand topologies, and sophisticated metric. EIGRP’s underlying processes and technologies—neighbor discovery/recovery mechanism, RTP,DUAL finite state machine, and protocol-dependent modules. EIGRPs tables—neighbor table, topology table, and routing table EIGRP terminology:• Advertised distance (the metric for an EIGRP neighbor router to reach the destination; the metric between the next-hop router and the destination)• Feasible distance (the sum of the AD from the next-hop neighbor, and the cost between the local router and the next-hop router)• Successor (a neighboring router that has a least-cost loop-free path to a destination, the lowest FD)• Feasible successor (a neighboring router that has a loop-free backup path to a destination).• Passive routes, those not undergoing recomputation; active routes, those undergoing recomputation The five EIGRP packet types: hello, update, query, reply, and acknowledgment.• Updates, queries, and replies are sent reliably.
  • Chapter 2172© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicChapter 2 Summary• EIGRP initial route discovery process, started by a router sending hello packets.Neighboring routers reply with update packets, which populate the routerstopology table. The router chooses the successor routes and offers them to therouting table.• The DUAL process including selecting FSs. To qualify as an FS, a next-hop routermust have an AD less than the FD of the current successor route for the particularnetwork, to ensure a loop-free network.• The EIGRP metric calculation, which defaults to bandwidth (the slowest bandwidthbetween the source and destination) + delay (the cumulative interface delayalong the path).• Planning EIGRP implementations, including:• IP addressing• Network topology• EIGRP traffic engineering.• The list of tasks for each router in the network include:• Enabling the EIGRP routing protocol (with the correct AS number)• Configuring the proper network statements• Optionally configuring the metric to appropriate interfaces.
  • Chapter 2173© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicChapter 2 Summary (continued)• Basic EIGRP configuration commands.• Commands for verifying EIGRP operation.• Configuring a passive-interface.• Propagating a default route.• EIGRP summarization.• EIGRP over Frame Relay.• EIGRP over MPLS.• EIGRP load-balancing• EIGRP operation in WAN environments:• Configuring, verifying, and troubleshooting EIGRP MD5 authentication.• EIGRP scalability factors, including the amount of information exchanged, the numberof routers, the depth of the topology, and the number of alternative paths through thenetwork.• The SIA state and how to limit the query range to help reduce SIAs.• Configuring the remote routers as stub EIGRP routers.• Graceful shutdown, which broadcasts a goodbye message (in a hello packet, with all Kvalues set to 255) when an EIGRP routing process is shut down, to inform neighbors
  • Chapter 2174© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco PublicResources http://www.cisco.com/go/eigrp http://www.cisco.com/en/US/customer/docs/ios/iproute_eigrp/command/reference/ire_book.html
  • Chapter 2175© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public