CCCNP ROUTE v6_ch02
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CCCNP ROUTE v6_ch02

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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.

CCCNP ROUTE v6_ch02 CCCNP ROUTE v6_ch02 Presentation Transcript

  • © 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public ROUTE v6 Chapter 2 1 Chapter 2: Configuring the Enhanced Interior Gateway Routing Protocol CCNP ROUTE: Implementing IP Routing
  • Chapter 2 2© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Chapter 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 2 3© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Understanding EIGRP Terminology and Operation
  • Chapter 2 4© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Capabilities and Attributes  EIGRP is a Cisco-proprietary distance-vector protocol with link-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 and topologies • By default, it performs automatic route summarization at major network boundaries (can be disabled) but can also be configured to summarize on interfaces.
  • Chapter 2 5© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Terminology  Neighbor table  Topology table  Routing table  Advertised Distance (AD)  Feasible Distance (FD)  Successor  Feasible successor (FS)  Passive Versus Active Routes
  • Chapter 2 6© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Tables  Neighbor table • Contains EIGRP neighbor addresses and the interface through which they can be reached.  Topology table • Contains all destinations advertised by neighboring routers.  Routing table • Contains EIGRP successor routes.
  • Chapter 2 7© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public AD versus FD  Advertised Distance (AD) • Advertised distance (AD), also referred to as the Reported Distance, 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 the next-hop router plus the next-hop router’s AD to the destination network.
  • Chapter 2 8© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Successor and Feasible Successor  Successor • A successor is a neighboring router that has a least-cost path to a destination (the lowest FD) that is guaranteed not to be part of a routing loop. • Successor routes are offered to the routing table to be used for forwarding 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 it is not the least-cost path. • A feasible successor ensures a loop-free topology because it must have an AD less than the FD of the current successor route. • Feasible successors are selected at the same time as successors but are kept in the topology table as backups to the successor routes. • The topology table can maintain multiple feasible successors for a destination.
  • Chapter 2 9© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Passive versus Active Routes  Passive Route • A route is considered passive when the router is not performing recomputation on that route. • Passive is the operational, stable state.  Active route • A route is active when it is undergoing recomputation.
  • Chapter 2 10© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Key EIGRP Technologies  Reliable Transport Protocol (RTP) • Responsible for guaranteed, ordered delivery of EIGRP packets to all neighbors.  Neighbor discovery/recovery mechanism • Enables EIGRP routers to dynamically learn when their neighbors become unreachable or inoperative by periodically sending small hello packets.  Protocol-dependent modules (PDMs) • Responsible for network layer protocol-specific requirements such as IP, IPv6, AppleTalk, and Novell NetWare.  DUAL finite-state machine • Diffusing Update Algorithm (DUAL) is the routing algorithm that tracks all routes advertised by all neighbors and uses distance information, known as the composite metric, to select efficient, loop-free paths to all destinations.
  • Chapter 2 11© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Reliable Transport Protocol  EIGRP cannot use the services of UDP or TCP since IPX and Appletalk do not use the TCP/IP protocol suite.  Reliable Transport Protocol (RTP) is the Transport layer protocol uniquely used by EIGRP for the delivery and reception of EIGRP packets. • RTP is similar to TCP but is a Cisco proprietary.  RTP provides reliable or unreliable service as the situation warrants. • Reliable packets (Update, Query, Reply) require explicit acknowledgement while unreliable packets (Hello, ACK) do not.
  • Chapter 2 12© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Neighbor Discovery / Recovery  EIGRP routers actively establish relationships with their neighbors.  Adjacencies are established using small Hello packets which are sent every 5 or 60 seconds. • If a neighbor misses 3 consecutive Hello packets then the route is considered invalid. • Default = 15 seconds or 180 seconds.
  • Chapter 2 13© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Neighbor Discovery / Recovery
  • Chapter 2 14© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Protocol-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 its specific routed protocol.
  • Chapter 2 15© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Protocol-Dependent Modules EIGRP maintains individual tables for each routed protocol.
  • Chapter 2 16© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public DUAL finite-state machine  DUAL uses the Neighbor and Topology tables to calculate route information.  When a link fails, DUAL looks for a feasible successor in its Neighbor and Topology tables. • It compares all routes advertised by neighbors by using a composite metric for each route. • Lowest-cost paths are then inserted into the routing table.
  • Chapter 2 17© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Packet Frame Header Frame Payload CRC IP Header Protocol Number (EIGRP = 88) EIGRP Header EIGRP Message On a LAN, the EIGRP packet is encapsulated in an Ethernet frame with a destination multicast MAC address: 01-00-5E-00-00-0A The destination IP address is set to the multicast 224.0.0.10 and the EIGRP protocol field is 88. The EIGRP header identifies the type of EIGRP packet and autonomous system number. The EIGRP message consists of the Type / Length / Value (TLV).
  • Chapter 2 18© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Header  EIGRP uses these 5 packet types to maintain its various tables and establish complex relationships with neighbor routers: • Hello • Acknowledgment • Update • Query • Reply
  • Chapter 2 19© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Header
  • Chapter 2 20© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Packet
  • Chapter 2 21© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Hello Packets  EIGRP relies on Hello packets to discover, verify, and rediscover neighbor routers.  EIGRP Hello packets are multicast to 224.0.0.10.  Hello packets are always sent unreliably and therefore do not require acknowledgment.
  • Chapter 2 22© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Hello Packets
  • Chapter 2 23© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Hello Packets  Hellos are sent at a fixed (and configurable) interval, called the 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 with bandwidth greater than T1, and LANs. • Low Bandwidth = 60 seconds • Default interval on T1 or less multipoint WAN circuits.
  • Chapter 2 24© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Hello Packets  On hearing Hellos, a router creates a neighbor table and the continued receipt of Hellos maintains the table.  Holdtime is the maximum amount of allowed time that Hellos 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 2 25© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Hello Packets T3
  • Chapter 2 26© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Acknowledgement Packets  Are used to indicate receipt of any EIGRP packet during a "reliable" (i.e., RTP) exchange. • To be reliable, a sender's message must be acknowledged by the recipient.  Acknowledgment packets are: • Dataless Hello packets. • Unicast.
  • Chapter 2 27© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Update Packets  After the local router discovers a new neighbor, update packets are sent to the new neighbor.  Update packets are also used when a router detects a topology change. • The router sends a multicast Update packet to all neighbors, alerting them to the change.  All Update packets are sent reliably.
  • Chapter 2 28© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Update Packets Update packet • Initially sent after a new neighbor is discovered. • Sent when a topology change has been detected.
  • Chapter 2 29© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Query and Reply Packets  Query and Reply packets are sent when a destination has no feasible successors.  Both packet types are sent reliably.  A Query packet is multicasted to other EIGRP routers during the route re-computation process. • Query packets are always multicast.  A Reply packet is used to respond to a query to instruct the originator not to recompute the route because feasible successors exist. • Reply packets are always unicast.
  • Chapter 2 30© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Query and Reply Packets
  • Chapter 2 31© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Message
  • Chapter 2 32© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Message - TLVs
  • Chapter 2 33© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public TLV 0x0001 - EIGRP Parameters • K values are used to calculate the EIGRP metric. • The Hold Time advertised by a neighbor is the maximum time a router should wait for any valid EIGRP message sent by that neighbor before declaring it dead.
  • Chapter 2 34© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public TLV 0x0002 - Internal IP Routes • Delay: Sum of delays in units of 10 microseconds from source to destination. • Bandwidth: Lowest configured bandwidth on any interface along the route. • Prefix length: Specifies the number of network bits in the subnet mask. • Destination: The destination address of the route.
  • Chapter 2 35© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public TLV 0x0003 - External IP Routes  IP external routes are routes which are imported into EIGRP through redistribution of a default route or other routing protocols. • Fields used to track external source of route. • Same fields contained in the Internal IP route TLV (0x0002).
  • Chapter 2 36© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Packet Types Packet Type Use Hello Used to discover other EIGRP routers in the network. Acknowledgement Used to acknowledge the receipt of any EIGRP packet. Update Convey routing information to known destinations. Query Used to get specific information from a neighbor router. Reply Used to respond to a query.
  • Chapter 2 37© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Initial Route Discovery
  • Chapter 2 38© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP 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 Table Neighbor IP Address Local router exit interface to neighbor IP EIGRP Topology Table Destination 1 FD / AD via each neighbor IP Routing Table Destination 1 Best route List of directly connected adjacent EIGRP neighbor routers and the local interface to exit to reach it. List of all routes learned from each EIGRP neighbor and identifies successor routes and feasible successor routes. List of the best (successor) routes from the EIGRP topology table and other routing processes.
  • Chapter 2 39© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Example: EIGRP Tables Router C’s tables:
  • Chapter 2 40© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public R1# show ip eigrp neighbors IP-EIGRP neighbors for process 100 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 0 192.168.1.102 Se0/0/1 11 00:07:22 10 2280 0 5 R1# EIGRP Neighbor Table Lists the order in which a peering session was established with the specified neighbor, starting with 0. Neighbor’s IP address Local interface receiving EIGRP Hello packets. Seconds remaining before declaring neighbor down. The current hold time and is reset to the maximum hold time whenever a Hello packet is received. SRTT (Smooth Round Trip Timer) and RTO (Retransmit Interval) are used by RTP to manage reliable EIGRP packets. SRTT indicates how long it takes for this neighbor to respond to reliable packets. RTO indicates how long to wait before retransmitting if no ACK is received. Queue count should always be zero otherwise there’s congestion on the link. The sequence number of the last update, query, or reply packet that was received from this neighbor. Amount of time since this neighbor was added to the neighbor table.
  • Chapter 2 41© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public R1# show ip eigrp topology IP-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 Status P 172.17.0.0/16, 1 successors, FD is 40514560 via 192.168.1.102 (40514560/28160), Serial0/0/1 R1# EIGRP Topology Table Indicates if the route is in passive or active state. Destination network. Number of successors Next-hop address for successor. Outbound interface to reach the network. Feasible distance (FD) to the successor Feasible distance (FD) to the successor Advertised distance (AD) from the successor
  • Chapter 2 42© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Routing Table EIGRP route Destination network R1# show ip route <output omitted> Gateway of last resort is not set D 172.17.0.0/16 [90/40514560] via 192.168.1.102, 00:02:22, Serial0/0/1 172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks D 172.16.0.0/16 is a summary, 00:31:31, Null0 C 172.16.1.0/24 is directly connected, FastEthernet0/0 R1# Administrative distance Feasible distance Next-hop address to reach the network Time indicating the last update packet received Local router exit interface to destination network Summary route automatically created as the result of the default classful behavior of EIGRP.
  • Chapter 2 43© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Administrative Distance (AD)  EIGRP default administrative distances Routes manually summarized. Routes redistributed into EIGRP.
  • Chapter 2 44© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public DUAL Example (1) 10.1.1.0 /24 A C B E D (2) (2) (1) (1) (1) EIGRP FD AD Topology 10.1.1.0 /24 3 ***** Passive ***** via B 3 1 Successor via D 4 2 Feasible Successor via E 4 3 Router C EIGRP FD AD Topology 10.1.1.0 /24 3 ***** Passive ***** via D 3 2 Successor via C 4 3 Router E EIGRP FD AD Topology 10.1.1.0 /24 2 ***** Passive ***** via B 2 1 Successor via C 5 3 Router D
  • Chapter 2 45© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public DUAL Example (1) 10.1.1.0 /24 A C B E D (2) (2) (1) (1) (1) EIGRP FD AD Topology 10.1.1.0 /24 3 ***** Passive ***** via B 3 1 Successor via D 4 2 Feasible Successor via E 4 3 Router C EIGRP FD AD Topology 10.1.1.0 /24 3 ***** Passive ***** via D 3 2 Successor via C 4 3 Router E EIGRP FD AD Topology 10.1.1.0 /24 2 ***** Passive ***** via B 2 1 Successor via C 5 3 Router D
  • Chapter 2 46© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public DUAL Example (1) 10.1.1.0 /24 A C B E D (2) (2) (1) (1) EIGRP FD AD Topology 10.1.1.0 /24 3 ***** Passive ***** via B 3 1 Successor via D 4 2 Feasible Successor via E 4 3 Router C EIGRP FD AD Topology 10.1.1.0 /24 3 ***** Passive ***** via D 3 2 Successor via C 4 3 Router E EIGRP FD AD Topology 10.1.1.0 /24 -1 ***** ACTIVE ****** via E (Q) Query via C 5 3 (Q) Query Router D Q Q Q = Query
  • Chapter 2 47© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public DUAL Example (1) 10.1.1.0 /24 A C B E D (2) (2) (1) (1) EIGRP FD AD Topology 10.1.1.0 /24 3 ***** Passive ***** via B 3 1 Successor via D via E 4 3 Router C EIGRP FD AD Topology 10.1.1.0 /24 -1 ***** ACTIVE ****** via D via C 4 3 (Q) Query Router E EIGRP FD AD Topology 10.1.1.0 /24 -1 ***** ACTIVE ****** via E (Q) Query via C 5 3 Router D R Q Q = Query R = Reply
  • Chapter 2 48© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public DUAL Example (1) 10.1.1.0 /24 A C B E D (2) (2) (1) (1) EIGRP FD AD Topology 10.1.1.0 /24 3 ***** Passive ***** via B 3 1 Successor via D via E Router C EIGRP FD AD Topology 10.1.1.0 /24 4 ***** Passive ***** via C 4 3 Successor via D Router E EIGRP FD AD Topology 10.1.1.0 /24 -1 ***** ACTIVE ****** via E (Q) Query via C 5 3 Router D R Q = Query R = Reply
  • Chapter 2 49© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public DUAL Example (1) 10.1.1.0 /24 A C B E D (2) (2) (1) (1) EIGRP FD AD Topology 10.1.1.0 /24 3 ***** Passive ***** via B 3 1 Successor via D via E Router C EIGRP FD AD Topology 10.1.1.0 /24 4 ***** Passive ***** via C 4 3 Successor via D Router E EIGRP FD AD Topology 10.1.1.0 /24 5 ***** Passive ***** via C 5 3 Successor via E 5 4 Successor Router D R Q = Query R = Reply
  • Chapter 2 50© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public DUAL Example (1) 10.1.1.0 /24 A C B E D (2) (2) (1) (1) EIGRP FD AD Topology 10.1.1.0 /24 3 ***** Passive ***** via B 3 1 Successor via D via E Router C EIGRP FD AD Topology 10.1.1.0 /24 4 ***** Passive ***** via C 4 3 Successor via D Router E EIGRP FD AD Topology 10.1.1.0 /24 5 ***** Passive ***** via C 5 3 Successor via E 5 4 Successor Router D
  • Chapter 2 51© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Metric Calculation  EIGRP uses a composite metric which can be based on the following 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 smallest MTU in the path. In actual fact, the MTU is included in the EIGRP routing update, but is not actually used in the metric calculation.
  • Chapter 2 52© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Bandwidth  EIGRP uses the slowest bandwidth (BW) in its metric calculation. • Calculated BW = reference BW / slowest BW (kbps)  The value of the bandwidth may or may not reflect the actual physical bandwidth of the interface. • For example, most serial interfaces use the default bandwidth value of 1.544 Mbps but this may not accurately reflect the links actual bandwidth.
  • Chapter 2 53© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Bandwidth  Because both EIGRP and OSPF use bandwidth in default metric calculations, a correct value for bandwidth is very important to the accuracy of routing information. • If the actual bandwidth of the link differs from the default bandwidth value, then the bandwidth value should be modified.  To modify the bandwidth value, use the bandwidth interface command. Note: The bandwidth command does NOT change the physical bandwidth of the link.
  • Chapter 2 54© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Delay  Delay is a measure of the time it takes for a packet to traverse a route. • EIGRP uses the cumulative sum of all outgoing interfaces. • Calculated Delay = the sum of outgoing interface delays / 10  The delay (DLY) metric is a static value based on the type of link to which the interface is connected and is expressed in microseconds.
  • Chapter 2 55© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Other EIGRP Metrics  Reliability (not a default EIGRP metric) is a measure of the likelihood 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 traffic is using a link • Number is determined dynamically and is expressed as a fraction of 255 • The lower the fraction the less the load on the link  These optional criteria can be used but are not recommended, because they typically result in frequent recalculation of the topology table.
  • Chapter 2 56© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Composite Metric Calculation  The EIGRP composite metric formula consists of values K1 through 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 k3 k4 k5
  • Chapter 2 57© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Mismatched 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 2 58© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Metric Calculation Example Slowest bandwidth: Plus the sum of the delays
  • Chapter 2 59© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Bandwidth Calculation Example  Bandwidth = 10,000,000 / 1024 = 9765 * 256 = 2499840
  • Chapter 2 60© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Delay Calculation Example  Delay = 20,000 / 10 + (100 / 10) * 256 = 514560
  • Chapter 2 61© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Metric Calculation Example  EIGRP Metric = 2499840 + 514560 = 3014400
  • Chapter 2 62© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Planning EIGRP Routing Implementations
  • Chapter 2 63© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Planning to Deploy EIGRP  Prior to deploying an EIGRP routing solution, the following should be considered: • IP addressing plan • Network topology • EIGRP traffic engineering  Once the requirements have been assessed, the implementation plan can be created.
  • Chapter 2 64© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Implementing EIGRP  The information necessary to implement EIGRP routing includes 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 traffic engineering.  In the implementation plan, EIGRP the tasks include the following: • Enabling the EIGRP routing protocol. • Configuring the proper network statements. • Optionally configuring the metric to appropriate interfaces.
  • Chapter 2 65© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Verifying EIGRP  After implementing EIGRP, verification should confirm proper deployment on each router.  Verification tasks include verifying: • The EIGRP neighbor relationships. • That the EIGRP topology table is populated with the necessary information. • That IP routing table is populated with the necessary information. • That there is connectivity in the network between routers and to other devices. • That EIGRP behaves as expected in a case of a topology change, by testing link failure and router failure events.
  • Chapter 2 66© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Documenting  After a successful EIGRP deployment, the solution and verification process and results should be documented for future 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 2 67© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Configuring and Verifying EIGRP
  • Chapter 2 68© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Enable EIGRP Routing  Define EIGRP as the IP routing protocol. Router(config)# router eigrp autonomous-system-id  To exchange routing updates, EIGRP routers must have the same autonomous system ID.
  • Chapter 2 69© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Identify 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 the address of a directly connected interface.  The mask is a wildcard mask (inverse mask) used to determine how to interpret the address. • The mask has wildcard bits, where 0 is a match and 1 is “don’t care.” • For example, 0.0.255.255 indicates a match in the first 2 octets.
  • Chapter 2 70© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Note on EIGRP Masks  Most EIGRP references state that the wildcard mask is required.  However, since IOS 12.0(4)T, the mask argument can actually be configured using wild card bits or a regular subnet mask.  For example, either format could be used to configure the 10.10.10.0 network: network 10.10.10.0 0.0.0.3 or network 10.10.10.0 255.255.255.252
  • Chapter 2 71© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Define the Interface Bandwidth  Defines the interface’s bandwidth (optional). Router(config-if)# bandwidth kilobits  The kilobits parameter indicates the intended bandwidth in kbps.  For example, to set the bandwidth to 512,000 bps, use the bandwidth 512 command.  The configured bandwidth is used by routing protocols in the metric calculation.  The command does not actually change the speed of the interface.
  • Chapter 2 72© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Enable / Disable Automatic Summarization  By default, EIGRP automatically summarizes subnets. Router(config-router)# auto-summary  This makes EIGRP behave like a classful routing protocol and therefore summarizes subnets on the classful boundary.  Automatic summarization can be disabled using the no auto-summary router configuration command.
  • Chapter 2 73© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Configuring EIGRP Example: Classful R1(config)# interface Fa0/0 R1(config-if)# ip address 172.16.1.1 255.255.255.0 R1(config-if)# no shut R1(config-if)# interface S0/0/0 R1(config-if)# ip address 192.168.1.101 255.255.255.224 R1(config-if)# bandwidth 64 R1(config-if)# no shut R1(config-if)# exit Classful configuration example: R2(config)# interface Fa0/0 R2(config-if)# ip address 172.16.2.1 255.255.255.0 R2(config-if)# no shut R2(config-if)# interface S0/0/0 R2(config-if)# ip address 192.168.1.102 255.255.255.224 R2(config-if)# bandwidth 64 R2(config-if)# no shut R2(config-if)# interface S0/0/1 R2(config-if)# ip address 192.168.1.1 255.255.255.224 R2(config-if)# bandwidth 64 R2(config-if)# no shut R2(config-if)# exit Fa0/0Fa0/0 R1 R2 172.16.1.0 /24 EIGRP AS 100 Internet 192.168.1.0 /27 S0/0/1 172.17.2.0 /24 S0/0/0 S0/0/0 64 kbps 192.168.1.96 /27 .101 .102 .1 .1.1
  • Chapter 2 74© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Configuring EIGRP Example: Classful R1(config)# router eigrp 100 R1(config-router)# network 192.168.1.96 R1(config-router)# network 172.16.1.0 R1(config-router)# Classful configuration example: R2(config)# router eigrp 100 R2(config-router)# network 192.168.1.96 R2(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) is up: new adjacency 172.17.2.0 R2(config-router)# R2# Fa0/0Fa0/0 R1 R2 172.16.1.0 /24 EIGRP AS 100 Internet 192.168.1.0 /27 S0/0/1 172.17.2.0 /24 S0/0/0 S0/0/0 64 kbps 192.168.1.96 /27 .101 .102 .1 .1.1
  • Chapter 2 75© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Verifying EIGRP Example R1# show running-config | section router eigrp router eigrp 100 network 172.16.0.0 network 192.168.1.0 auto-summary R1# show ip route <output omitted> Gateway of last resort is not set D 172.17.0.0/16 [90/40514560] via 192.168.1.102, 00:24:02, Serial0/0/0 172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks D 172.16.0.0/16 is a summary, 00:25:27, Null0 C 172.16.1.0/24 is directly connected, FastEthernet0/0 192.168.1.0/24 is variably subnetted, 3 subnets, 2 masks C 192.168.1.96/27 is directly connected, Serial0/0/0 D 192.168.1.0/27 [90/41024000] via 192.168.1.102, 00:16:56, Serial0/0/0 D 192.168.1.0/24 is a summary, 00:25:27, Null0 R1# R1 Classful configuration example: Fa0/0Fa0/0 R1 R2 172.16.1.0 /24 EIGRP AS 100 Internet 192.168.1.0 /27 S0/0/1 172.17.2.0 /24 S0/0/0 S0/0/0 64 kbps 192.168.1.96 /27 .101 .102 .1 .1.1
  • Chapter 2 76© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Verifying EIGRP Example R2# show running-config | section router eigrp router eigrp 100 network 172.17.0.0 network 192.168.1.0 auto-summary R2# show ip route <output omitted> Gateway of last resort is not set 172.17.0.0/16 is variably subnetted, 2 subnets, 2 masks D 172.17.0.0/16 is a summary, 00:13:10, Null0 C 172.17.2.0/24 is directly connected, FastEthernet0/0 D 172.16.0.0/16 [90/40514560] via 192.168.1.101, 00:13:26, Serial0/0/0 192.168.1.0/24 is variably subnetted, 3 subnets, 2 masks C 192.168.1.96/27 is directly connected, Serial0/0/0 C 192.168.1.0/27 is directly connected, Serial0/0/1 D 192.168.1.0/24 is a summary, 00:13:10, Null0 R2# R2 Classful configuration example: Fa0/0Fa0/0 R1 R2 172.16.1.0 /24 EIGRP AS 100 Internet 192.168.1.0 /27 S0/0/1 172.17.2.0 /24 S0/0/0 S0/0/0 64 kbps 192.168.1.96 /27 .101 .102 .1 .1.1
  • Chapter 2 77© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Verifying EIGRP Example R2# show ip protocols Routing Protocol is "eigrp 100" <output omitted> Automatic network summarization is in effect Automatic address summarization: 192.168.1.0/24 for FastEthernet0/0 Summarizing with metric 40512000 172.17.0.0/16 for Serial0/0/0, Serial0/0/1 Summarizing with metric 28160 Maximum path: 4 Routing for Networks: 172.17.0.0 192.168.1.0 Routing Information Sources: <output omitted> R2# Classful configuration example: Fa0/0Fa0/0 R1 R2 172.16.1.0 /24 EIGRP AS 100 Internet 192.168.1.0 /27 S0/0/1 172.17.2.0 /24 S0/0/0 S0/0/0 64 kbps 192.168.1.96 /27 .101 .102 .1 .1.1
  • Chapter 2 78© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Configuring EIGRP Example: Classless Classless configuration example: R2(config)# no router eigrp 100 R2(config)# router eigrp 100 R2(config-router)# network 192.168.1.96 0.0.0.31 R2(config-router)# network 172.17.2.0 0.0.0.255 R2(config-router)# end R2# show run | section router eigrp router eigrp 100 network 172.17.2.0 0.0.0.255 network 192.168.1.96 0.0.0.31 auto-summary R2# Fa0/0Fa0/0 172.17.2.0 /24 R1 R2 172.16.1.0 /24 EIGRP AS 100 Internet 192.168.1.0 /27 64 kbps 192.168.1.96 /27 .101 .102 S0/0/1 S0/0/0 S0/0/0 .1 .1.1 R1(config)# no router eigrp 100 R1(config)# router eigrp 100 R1(config-router)# network 192.168.1.96 0.0.0.31 R1(config-router)# network 172.16.1.0 0.0.0.255 R1(config-router)# end R1# show run | section router eigrp router eigrp 100 network 172.16.1.0 0.0.0.255 network 192.168.1.96 0.0.0.31 auto-summary R1#
  • Chapter 2 79© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Verifying EIGRP Example R2# show ip protocols Routing Protocol is "eigrp 100" <output omitted> Automatic network summarization is in effect Automatic address summarization: 192.168.1.0/24 for FastEthernet0/0 Summarizing with metric 40512000 172.17.0.0/16 for Serial0/0/0 Summarizing with metric 28160 Maximum path: 4 Routing for Networks: 172.17.2.0/24 192.168.1.96/27 Routing Information Sources: Gateway Distance Last Update (this router) 90 00:00:06 Gateway Distance Last Update 192.168.1.101 90 00:00:26 Distance: internal 90 external 170 Classful configuration example: Fa0/0Fa0/0 R1 R2 172.16.1.0 /24 EIGRP AS 100 Internet 192.168.1.0 /27 S0/0/1 172.17.2.0 /24 S0/0/0 S0/0/0 64 kbps 192.168.1.96 /27 .101 .102 .1 .1.1
  • Chapter 2 80© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Verifying EIGRP: show ip protocols R1# show ip protocols Routing Protocol is "eigrp 100" <output omitted> EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0 EIGRP maximum hopcount 100 EIGRP maximum metric variance 1 Redistributing: eigrp 100 EIGRP NSF-aware route hold timer is 240s Automatic network summarization is in effect Automatic address summarization: 192.168.1.0/24 for FastEthernet0/0 Summarizing with metric 40512000 172.16.0.0/16 for Serial0/0/0 Summarizing with metric 28160 Maximum path: 4 Routing for Networks: 172.16.1.0/24 192.168.1.96/27 Routing Information Sources: Gateway Distance Last Update (this router) 90 00:08:56 Gateway Distance Last Update 192.168.1.102 90 00:07:59 Distance: internal 90 external 170 Verify routing protocol information on the router.
  • Chapter 2 81© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Verifying EIGRP: show ip eigrp neighbors R1# show ip eigrp neighbors IP-EIGRP neighbors for process 100 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 0 192.168.1.102 Se0/0/0 11 00:09:17 22 2280 0 5 R1# EIGRP uses the Neighbor table to list adjacent routers.
  • Chapter 2 82© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Verifying EIGRP: show ip eigrp topology R1# show ip eigrp topology IP-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 Status P 192.168.1.96/27, 1 successors, FD is 40512000 via Connected, Serial0/0/0 P 192.168.1.0/24, 1 successors, FD is 40512000 via Summary (40512000/0), Null0 P 172.16.0.0/16, 1 successors, FD is 28160 via Summary (28160/0), Null0 P 172.17.0.0/16, 1 successors, FD is 40514560 via 192.168.1.102 (40514560/28160), Serial0/0/0 P 172.16.1.0/24, 1 successors, FD is 28160 via Connected, FastEthernet0/0 R1# Verify routing protocol information on the router.
  • Chapter 2 83© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Verifying EIGRP: show ip route eigrp R1# show ip route eigrp D 172.17.0.0/16 [90/40514560] via 192.168.1.102, 00:10:18, Serial0/0/0 172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks D 172.16.0.0/16 is a summary, 00:11:19, Null0 192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks D 192.168.1.0/24 is a summary, 00:11:19, Null0 R1# R1# show ip route <output omitted> Gateway of last resort is not set D 172.17.0.0/16 [90/40514560] via 192.168.1.102, 00:10:35, Serial0/0/0 172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks D 172.16.0.0/16 is a summary, 00:11:37, Null0 C 172.16.1.0/24 is directly connected, FastEthernet0/0 192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks C 192.168.1.96/27 is directly connected, Serial0/0/0 D 192.168.1.0/24 is a summary, 00:11:37, Null0 R1# Verify that the router recognizes EIGRP routes.
  • Chapter 2 84© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Verifying EIGRP: show ip eigrp interfaces R1# show ip eigrp interfaces IP-EIGRP interfaces for process 100 Xmit Queue Mean Pacing Time Multicast Pending Interface Peers Un/Reliable SRTT Un/Reliable Flow Timer Routes Se0/0/0 1 0/0 22 10/380 468 0 Fa0/0 0 0/0 0 0/1 0 0 R1# Verify EIGRP configured interfaces.
  • Chapter 2 85© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Verifying EIGRP: show ip eigrp traffic R1# show ip eigrp traffic IP-EIGRP Traffic Statistics for AS 100 Hellos sent/received: 338/166 Updates sent/received: 7/7 Queries sent/received: 0/0 Replies sent/received: 0/0 Acks sent/received: 2/2 SIA-Queries sent/received: 0/0 SIA-Replies sent/received: 0/0 Hello Process ID: 228 PDM Process ID: 226 IP 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 2 86© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Verifying EIGRP: debug eigrp packets R2# 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/re ly 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/re ly 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/re ly 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 FastEthernet0/0 Traces transmission and receipt of EIGRP packets.
  • Chapter 2 87© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP 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 2 88© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Passive-Interface Example R1(config)# router eigrp 100 R1(config-router)# passive-interface fa0/0 R1(config-router)# R2(config)# router eigrp 100 R2(config-router)# passive-interface fa0/0 R2(config-router)# Alternate configuration: R1(config)# router eigrp 100 R1(config-router)# passive-interface default R1(config-router)# no passive-interface S0/0/0 R2(config)# router eigrp 100 R2(config-router)# passive-interface default R2(config-router)# no passive-interface S0/0/0 Fa0/0Fa0/0 R1 R2 172.16.1.0 /24 EIGRP AS 100 Internet 192.168.1.0 /27 172.17.2.0 /24 64 kbps 192.168.1.96 /27 .101 .102 S0/0/1 S0/0/0 S0/0/0 .1 .1.1
  • Chapter 2 89© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Propagating a Default Route  To propagate a default route in EIGRP, use either the: ip default-network network-number global configuration command. Or ip route 0.0.0.0 0.0.0.0 next-hop | interface router configuration command.  Once configured, the default route has to be propagated into the EIGRP AS.
  • Chapter 2 90© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public ip default-network Command  Configures a router to advertise a network as the gateway of last resort. Router(config)# ip default-network network  Other routers use their next-hop address to the advertised network as their default route.  There is no parameter to specify the subnet mask therefore the command 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 EIGRP routers in the AS.  A static route, then the static route must be redistributed into EIGRP.
  • Chapter 2 91© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public ip default-network Example R2# show ip route <output omitted> Gateway of last resort is not set 172.17.0.0/16 is variably subnetted, 2 subnets, 2 masks D 172.17.0.0/16 is a summary, 02:27:56, Null0 C 172.17.2.0/24 is directly connected, FastEthernet0/0 D 172.16.0.0/16 [90/40514560] via 192.168.1.101, 02:27:56, Serial0/0/0 192.168.1.0/27 is subnetted, 2 subnets C 192.168.1.96 is directly connected, Serial0/0/0 C 192.168.1.0 is directly connected, Serial0/0/1 R2# R1# show ip route <output omitted> Gateway of last resort is not set <output omitted> Fa0/0Fa0/0 R1 R2 172.16.1.0 /24 64 kbps EIGRP AS 100 Internet 172.31.0.0 /16192.168.1.96 /27 172.17.2.0 /24 .101 .102 S0/0/1 S0/0/0 S0/0/0 .1 .1.1 192.168.1.0 /27 .2
  • Chapter 2 92© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public ip default-network Example Fa0/0Fa0/0 R1 R2 172.16.1.0 /24 64 kbps EIGRP AS 100 Internet 172.31.0.0 /16192.168.1.96 /27 172.17.2.0 /24 .101 .102 S0/0/1 S0/0/0 S0/0/0 .1 .1.1 192.168.1.0 /27 .2 R2(config)# ip route 172.31.0.0 255.255.0.0 192.168.1.2 R2(config)# do ping 172.31.0.0 <output omitted> Success rate is 100 percent (5/5), round-trip min/avg/max = 28/28/28 ms R2(config)# ip default-network 172.31.0.0 R2(config)# router eigrp 100 R2(config-router)# redistribute static R2(config-router)# end R2#
  • Chapter 2 93© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public ip default-network Example R2# 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 192.168.1.2 192.168.1.0/27 is subnetted, 2 subnets C 192.168.1.96 is directly connected, Serial0/0/0 C 192.168.1.0 is directly connected, Serial0/0/1 R2# Fa0/0Fa0/0 R1 R2 172.16.1.0 /24 64 kbps EIGRP AS 100 Internet 172.31.0.0 /16192.168.1.96 /27 172.17.2.0 /24 .101 .102 S0/0/1 S0/0/0 S0/0/0 .1 .1.1 192.168.1.0 /27 .2 R1# 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, Serial0/0/0 192.168.1.0/27 is subnetted, 1 subnets C 192.168.1.96 is directly connected, Serial0/0/0 R1#
  • Chapter 2 94© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public ip 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 last resort. 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 0.0.0.0 needs to also be entered.  If the next-hop parameter is used, then the network 0.0.0.0 and the redistribute static command must be configured.
  • Chapter 2 95© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public ip route 0.0.0.0 0.0.0.0 interface Example Fa0/0Fa0/0 R1 R2 172.16.1.0 /24 64 kbps EIGRP AS 100 Internet 172.31.0.0 /16192.168.1.96 /27 172.17.2.0 /24 .101 .102 S0/0/1 S0/0/0 S0/0/0 .1 .1.1 192.168.1.0 /27 .2 R2(config)# ip route 0.0.0.0 0.0.0.0 S0/0/1 R2(config)# router eigrp 100 R2(config-router)# network 0.0.0.0 R2(config-router)# do show ip route <output omitted> Gateway of last resort is 0.0.0.0 to network 0.0.0.0 172.17.0.0/16 is variably subnetted, 2 subnets, 2 masks D 172.17.0.0/16 is a summary, 03:13:25, Null0 C 172.17.2.0/24 is directly connected, FastEthernet0/0 D 172.16.0.0/16 [90/40514560] via 192.168.1.101, 03:13:25, Serial0/0/0 192.168.1.0/27 is subnetted, 2 subnets C 192.168.1.96 is directly connected, Serial0/0/0 C 192.168.1.0 is directly connected, Serial0/0/1 S* 0.0.0.0/0 is directly connected, Serial0/0/1 R2(config-router)#
  • Chapter 2 96© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public ip route 0.0.0.0 0.0.0.0 next-hop Example Fa0/0Fa0/0 R1 R2 172.16.1.0 /24 64 kbps EIGRP AS 100 Internet 172.31.0.0 /16192.168.1.96 /27 172.17.2.0 /24 .101 .102 S0/0/1 S0/0/0 S0/0/0 .1 .1.1 192.168.1.0 /27 .2 R2(config)# ip route 0.0.0.0 0.0.0.0 192.168.1.2 R2(config)# router eigrp 100 R2(config-router)# network 0.0.0.0 R2(config-router)# redistribute static R2(config-router)# do show ip route <output omitted> Gateway of last resort is 192.168.1.2 to network 0.0.0.0 172.17.0.0/16 is variably subnetted, 2 subnets, 2 masks D 172.17.0.0/16 is a summary, 02:53:48, Null0 C 172.17.2.0/24 is directly connected, FastEthernet0/0 D 172.16.0.0/16 [90/40514560] via 192.168.1.101, 02:53:48, Serial0/0/0 192.168.1.0/27 is subnetted, 2 subnets C 192.168.1.96 is directly connected, Serial0/0/0 C 192.168.1.0 is directly connected, Serial0/0/1 S* 0.0.0.0/0 [1/0] via 192.168.1.2 R2(config-router)#
  • Chapter 2 97© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Route Summarization  EIGRP automatically summarizes routes at a major network boundary by default. • Due to the pre-configured auto-summary router configuration command. • In most cases, auto summarization is a good thing as it keeps routing tables as compact as possible. • Sometimes it’s not a good thing such as when there is a discontiguous subnetwork.  Typically for routing to work properly, auto-summarization should be disabled using the no auto-summary router configuration command.
  • Chapter 2 98© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Summarization in Discontiguous Networks R1 R2 10.10.10.0 /24 EIGRP AS 100 192.168.1.96 /30 10.20.20.0 /24  EIGRP Update: Connected to 10.0.0.0 /8 R1# show running-config | section router eigrp router eigrp 100 passive-interface FastEthernet0/0 network 10.10.10.0 0.0.0.255 network 192.168.1.96 0.0.0.31 auto-summary R1# show ip protocols Routing Protocol is "eigrp 100" <output omitted> Automatic network summarization is in effect Automatic address summarization: 10.0.0.0/8 for Serial0/0/0 Summarizing with metric 28160 Maximum path: 4 Routing for Networks: 10.10.10.0/24 192.168.1.96/27 Passive Interface(s): FastEthernet0/0 <output omitted>
  • Chapter 2 99© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Summarization in Discontiguous Networks R2# show ip route <output omitted> Gateway of last resort is 192.168.1.2 to network 0.0.0.0 10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks C 10.20.20.0/24 is directly connected, FastEthernet0/0 D 10.0.0.0/8 is a summary, 00:13:35, Null0 192.168.1.0/27 is subnetted, 2 subnets C 192.168.1.96 is directly connected, Serial0/0/0 C 192.168.1.0 is directly connected, Serial0/0/1 S* 0.0.0.0/0 [1/0] via 192.168.1.2 R2# R1 R2 10.10.10.0 /24 EIGRP AS 100 192.168.1.96 /30 10.20.20.0 /24  EIGRP Update: Connected to 10.0.0.0 /8 R2 ignores the R1 update because it is already connected to the classful 10.0.0.0/8 network.
  • Chapter 2 100© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Null 0  Notice that the summarized route (10.0.0.0/8) has an entry pointing to null0. • Null0 is automatically added to the table and 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. R2# show ip route <output omitted> Gateway of last resort is 192.168.1.2 to network 0.0.0.0 10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks C 10.20.20.0/24 is directly connected, FastEthernet0/0 D 10.0.0.0/8 is a summary, 00:13:35, Null0 192.168.1.0/27 is subnetted, 2 subnets C 192.168.1.96 is directly connected, Serial0/0/0 C 192.168.1.0 is directly connected, Serial0/0/1 S* 0.0.0.0/0 [1/0] via 192.168.1.2 R2#
  • Chapter 2 101© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Disabling Automatic Summarization R1 R2 10.10.10.0 /24 EIGRP AS 100 192.168.1.96 /30 10.20.20.0 /24  EIGRP Update: Connected to 10.0.0.0 /8 R1(config)# router eigrp 100 R1(config-router)# no auto-summary R1(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 configured R1(config-router)# end R1# show ip protocols Routing Protocol is "eigrp 100“ <output omitted> Automatic network summarization is not in effect Maximum path: 4 Routing for Networks: 10.10.10.0/24 192.168.1.96/27 <output omitted>
  • Chapter 2 102© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Disable Automatic Summarization R1 R2 10.10.10.0 /24 EIGRP AS 100 192.168.1.96 /30 10.20.20.0 /24  EIGRP Update: Connected to 10.0.0.0 /8 R2(config)# router eigrp 100 R2(config)# no auto-summary R2(config)# end R2# show ip route <output omitted> Gateway of last resort is 192.168.1.2 to network 0.0.0.0 10.0.0.0/24 is subnetted, 2 subnets C 10.20.20.0 is directly connected, FastEthernet0/0 D 10.10.10.0 [90/40514560] via 192.168.1.101, 00:05:21, Serial0/0/0 192.168.1.0/27 is subnetted, 2 subnets C 192.168.1.96 is directly connected, Serial0/0/0 C 192.168.1.0 is directly connected, Serial0/0/1 S* 0.0.0.0/0 [1/0] via 192.168.1.2 R2#
  • Chapter 2 103© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Summarizing on an Interface  Earlier distance vector protocols were unable to create summary routes other than the classful boundaries or /8, /16/ or /24.  To address this shortcoming, EIGRP added the ip summary-address eigrp interface configuration command. • The command is used to create one or more summary routes within a network on any bit boundary (as long as a more specific route exists in the routing table).  IP EIGRP summary routes are given an administrative distance value of 5. • Standard EIGRP routes receive an administrative distance of 90 • External EIGRP routes receive an administrative distance of 170.
  • Chapter 2 104© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public ip 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 Description as-number The number of the EIGRP AS is identified. address The IP address being advertised as the summary address. This address does not need to be aligned on Class A, B, or C boundaries. mask The IP subnet mask used to create the summary address. admin-distance (Optional) Administrative distance. A value from 0 to 255.
  • Chapter 2 105© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Route Summarization R1(config)# router eigrp 100 R1(config)# no auto-summary R2(config)# router eigrp 100 R2(config)# no auto-summary Fa0/0Fa0/0 R1 R2 10.10.10.0 /24 EIGRP AS 100 WAN 192.168.3.1 S0/0/0 10.10.20.0 /24 10.0.0.0 /8 R3 R3(config)# interface S0/0/0 R3(config-if)# ip address 192.168.3.1 255.255.255.0 R3(config-if)# ip summary-address eigrp 1 10.10.0.0 255.255.0.0 R3(config-if)# no shut R3(config-if)# exit R3# show ip protocols Routing Protocol is "eigrp 100" <output omitted> Automatic network summarization is not in effect Address Summarization: 10.10.0.0/16 for Serial0/0/0 <output omitted>
  • Chapter 2 106© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Configuring and Verifying EIGRP in an Enterprise WAN
  • Chapter 2 107© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP and WAN Considerations  There are various deployment options available for supporting 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 2 108© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Frame 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 the devices at the other ends of the PVCs to the local DLCI number.  Consists of three steps: 1. Configure an IP address on the serial interface. 2. Change the encapsulation on an interface using the encapsulation frame-relay command. 3. Activate the interface.
  • Chapter 2 109© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Frame Relay Using Dynamic Mapping R1(config)# interface S0/0/0 R1(config-if)# encapsulation frame-relay R1(config-if)# ip address 192.168.1.101 255.255.255.0 R1(config-if)# exit R1(config)# router eigrp 100 R1(config-router)# network 172.16.1.0 0.0.0.255 R1(config-router)# network 192.168.1.0 R1(config-router)# R3(config)# interface S0/0/0 R3(config-if)# encapsulation frame-relay R3(config-if)# ip address 192.168.1.103 255.255.255.0 R3(config-if)# exit R3(config)# router eigrp 100 R3(config-router)# network 172.16.3.0 0.0.0.255 R3(config-router)# network 192.168.1.0 R3(config-router)# Fa0/0 R1 172.16.1.0 /24 EIGRP AS 100 Frame Relay R2 R3 S0/0/0 192.168.1.0 /24 .101 .103 .102 S0/0/0 S0/0/0 DLCI 103 DLCI 102 DLCI 201 DLCI 301 Fa0/0 172.16.2.0 /24 Fa0/0 172.16.3.0 /24
  • Chapter 2 110© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Frame Relay Using Dynamic Mapping R1# show ip eigrp neighbors IP-EIGRP neighbors for process 100 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 0 192.168.1.102 Se0/0/0 10 00:07:22 10 2280 0 5 1 192.168.1.103 Se0/0/0 10 00:09:34 10 2320 0 9 R1# R3# show ip eigrp neighbors IP-EIGRP neighbors for process 100 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 0 192.168.1.101 Se0/0/0 10 00:11:45 10 1910 0 6 R3# Fa0/0 R1 172.16.1.0 /24 EIGRP AS 100 Frame Relay R2 R3 S0/0/0 192.168.1.0 /24 .101 .103 .102 S0/0/0 S0/0/0 DLCI 103 DLCI 102 DLCI 201 DLCI 301 Fa0/0 172.16.2.0 /24 Fa0/0 172.16.3.0 /24
  • Chapter 2 111© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Frame 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 the encapsulation frame-relay command. 3. Map the IP-to-DLCI mapping commands on the interface using the frame-relay map command. 4. Activate the interface.
  • Chapter 2 112© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public frame-relay map Command  Statically map the remote router's IP address to the local DLCI. Router(config-if)# frame-relay map protocol protocol-address dlci [broadcast] [ietf | cisco] [payload-compress {packet-by-packet | frf9 stack}] Parameter Description protocol 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 of dynamic 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 Stacker method, a Cisco proprietary compression method. frf9 stac (Optional) Enables FRF.9 compression using the Stacker method.
  • Chapter 2 113© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Frame Relay Using Static Mapping R1(config)# interface S0/0/0 R1(config-if)# encapsulation frame-relay R1(config-if)# ip address 192.168.1.101 255.255.255.0 R1(config-if)# frame-relay map ip 192.168.1.101 101 R1(config-if)# frame-relay map ip 192.168.1.102 102 broadcast R1(config-if)# frame-relay map ip 192.168.1.103 103 broadcast R1(config-if)# R3(config)# interface S0/0/0 R3(config-if)# encapsulation frame-relay R3(config-if)# ip address 192.168.1.103 255.255.255.0 R3(config-if)# frame-relay map ip 192.168.1.101 301 R3(config-if)# frame-relay map ip 192.168.1.102 301 broadcast R3(config-if)# frame-relay map ip 192.168.1.103 301 broadcast R3(config-if)# Fa0/0 R1 172.16.1.0 /24 EIGRP AS 100 Frame Relay R2 R3 S0/0/0 192.168.1.0 /24 .101 .103 .102 S0/0/0 S0/0/0 DLCI 103 DLCI 102 DLCI 201 DLCI 301 Fa0/0 172.16.2.0 /24 Fa0/0 172.16.3.0 /24
  • Chapter 2 114© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Frame Relay Using Static Mapping R1# show ip eigrp neighbors IP-EIGRP neighbors for process 100 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 0 192.168.1.102 Se0/0/0 10 00:06:20 10 2280 0 5 1 192.168.1.103 Se0/0/0 10 00:08:31 10 2320 0 9 R3# show ip eigrp neighbors IP-EIGRP neighbors for process 100 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 0 192.168.1.101 Se0/0/0 10 00:10:44 10 1910 0 6 1 192.168.1.102 Se0/0/0 10 00:03:02 10 2210 0 3 Fa0/0 R1 172.16.1.0 /24 EIGRP AS 100 Frame Relay R2 R3 S0/0/0 192.168.1.0 /24 .101 .103 .102 S0/0/0 S0/0/0 DLCI 103 DLCI 102 DLCI 201 DLCI 301 Fa0/0 172.16.2.0 /24 Fa0/0 172.16.3.0 /24
  • Chapter 2 115© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP over FR Multipoint Subinterfaces  Multipoint subinterfaces can be created using a single Frame Relay physical interface. • Uses a single subnet, preserving the IP address space.  Frame Relay multipoint is applicable to partial mesh and full mesh topologies.  Consists of several steps: • Configure the physical interface with no IP address and change the encapsulation 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 the frame-relay map command. • Either rely on dynamic mapping or configure a local DLCI value using the frame-relay interface-dlci command.
  • Chapter 2 116© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP over FR Multipoint Subinterfaces  Multipoint subinterfaces are configured with the interface serial number.subinterface-number multipoint command.  The IP address-to-DLCI mapping is done by either: • Specifying the local DLCI value (using the frame-relay interface-dlci dlci command) and relying on Inverse ARP • Using manual IP address-to-DLCI mapping.
  • Chapter 2 117© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP over FR Multipoint Subinterfaces Fa0/0 R1 172.16.1.0 /24 EIGRP AS 100 Frame Relay R2 R3 192.168.1.0 /24 .103 .102 S0/0/0.1 S0/0/0.1 DLCI 103 DLCI 102 DLCI 201 DLCI 301 Fa0/0 172.16.2.0 /24 Fa0/0 172.16.3.0 /24 S0/0/0.1 .101 R1(config)# interface S0/0/0 R1(config-if)# no ip address R1(config-if)# encapsulation frame-relay R1(config-if)# exit R1(config)# interface Serial0/0/0.1 multipoint R1(config-subif)# ip address 192.168.1.101 255.255.255.0 R1(config-subif)# no ip split-horizon eigrp 100 R1(config-subif)# frame-relay map ip 192.168.1.101 101 R1(config-subif)# frame-relay map ip 192.168.1.102 102 broadcast R1(config-subif)# frame-relay map ip 192.168.1.103 103 broadcast R1(config-subif)#
  • Chapter 2 118© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP over FR Multipoint Subinterfaces R1# show ip eigrp neighbors IP-EIGRP neighbors for process 100 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 0 192.168.1.102 Se0/0/0.1 10 00:06:41 10 2280 0 5 1 192.168.1.103 Se0/0/0.1 10 00:08:52 10 2320 0 9 R3# show ip eigrp neighbors IP-EIGRP neighbors for process 100 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 0 192.168.1.101 Se0/0/0.1 10 00:10:37 10 1910 0 6 1 192.168.1.102 Se0/0/0.1 10 00:03:12 10 2210 0 3 Fa0/0 R1 172.16.1.0 /24 EIGRP AS 100 Frame Relay R2 R3 192.168.1.0 /24 .103 .102 S0/0/0.1 S0/0/0.1 DLCI 103 DLCI 102 DLCI 201 DLCI 301 Fa0/0 172.16.2.0 /24 Fa0/0 172.16.3.0 /24 S0/0/0.1 .101
  • Chapter 2 119© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Unicast Neighbors  Define a neighboring router to exchange EIGRP routing information. Router(config-router)# neighbor {ip-address | ipv6-address} interface-type interface-number  EIGRP exchanges routing information with the specified neighbor using unicast packets.  Multiple neighbor statements can be used to establish peering sessions with multiple specific EIGRP neighbors.  The interface through which EIGRP will exchange routing updates must be specified in the neighbor statement.  The interfaces through which two EIGRP neighbors exchange routing updates must be configured with IP addresses from the same network.
  • Chapter 2 120© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Unicast Neighbors Fa0/0 R1 172.16.1.0 /24 EIGRP AS 100 Frame Relay R2 R3 192.168.1.0 /24 .103 .102 S0/0/0.1 S0/0/0.1 DLCI 103 DLCI 102 DLCI 201 DLCI 301 Fa0/0 172.16.2.0 /24 Fa0/0 172.16.3.0 /24 S0/0/0.1 .101 R1(config)# interface S0/0/0 R1(config-if)# no ip address R1(config-if)# encapsulation frame-relay R1(config-if)# interface S0/0/0.1 multipoint R1(config-subif)# ip address 192.168.1.101 255.255.255.0 R1(config-subif)# frame-relay map ip 192.168.1.102 102 broadcast R1(config-subif)# frame-relay map ip 192.168.1.103 103 broadcast R1(config-subif)# router eigrp 100 R1(config-router)# neighbor 192.168.1.102 S0/0/0.1 R1(config-router)#
  • Chapter 2 121© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Unicast Neighbors Fa0/0 R1 172.16.1.0 /24 EIGRP AS 100 Frame Relay R2 R3 192.168.1.0 /24 .103 .102 S0/0/0.1 S0/0/0.1 DLCI 103 DLCI 102 DLCI 201 DLCI 301 Fa0/0 172.16.2.0 /24 Fa0/0 172.16.3.0 /24 S0/0/0.1 .101 R2(config)# interface S0/0/0 R2(config-if)# no ip address R2(config-if)# encapsulation frame-relay R2(config-if)# interface S0/0/0.1 multipoint R2(config-subif)# ip address 192.168.1.102 255.255.255.0 R2(config-subif)# frame-relay map ip 192.168.1.101 201 broadcast R2(config-subif)# router eigrp 100 R2(config-router)# neighbor 192.168.1.101 S0/0/0.1 R2(config-router)#
  • Chapter 2 122© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP over FR Point-to-Point Subinterfaces  Point-to-point subinterfaces can be created using a single Frame Relay physical interface. • Uses multiple subnets.  Frame Relay point-to point is applicable to hub and spoke topologies.  Consists of several steps: • Configure the physical interface with no IP address and change the encapsulation 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 2 123© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP over FR Point-to-Point Subinterfaces  Multipoint subinterfaces are configured with the interface serial number.subinterface-number point-to-point command.  The IP address-to-DLCI mapping is done by either: • Specifying the local DLCI value (using the frame-relay interface-dlci dlci command) and relying on Inverse ARP.
  • Chapter 2 124© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP over FR Point-to-Point Subinterfaces R1(config)# interface S0/0/0 R1(config-if)# no ip address R1(config-if)# encapsulation frame-relay R1(config-if)# exit R1(config)# interface Serial0/0/0.2 point-to-point R1(config-subif)# ip address 192.168.2.101 255.255.255.0 R1(config-subif)# frame-relay interface-dlci 102 R1(config-subif)# R1(config-subif)# interface Serial0/0/0.3 point-to-point R1(config-subif)# ip address 192.168.3.101 255.255.255.0 R1(config-subif)# frame-relay interface-dlci 103 R1(config-subif)# Fa0/0 R1 172.16.1.0 /24 EIGRP AS 100 Frame Relay R2 R3 192.168.3.103 S0/0/0.1 S0/0/0.1 DLCI 103 DLCI 102 DLCI 201 DLCI 301 Fa0/0 172.16.2.0 /24 Fa0/0 172.16.3.0 /24 S0/0/0.3=192.168.3.101/24 192.168.2.102 S0/0/0.2=192.168.2.101/24
  • Chapter 2 125© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP over FR Point-to-Point Subinterfaces R1# show ip eigrp neighbors IP-EIGRP neighbors for process 100 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 0 192.168.2.102 Se0/0/0.2 10 00:08:04 10 2280 0 5 1 192.168.3.103 Se0/0/0.3 10 00:10:12 10 2320 0 9 R3# show ip eigrp neighbors IP-EIGRP neighbors for process 100 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 0 192.168.3.101 Se0/0/0.1 10 00:13:25 10 1910 0 6 Fa0/0 R1 172.16.1.0 /24 EIGRP AS 100 Frame Relay R2 R3 192.168.3.103 S0/0/0.1 S0/0/0.1 DLCI 103 DLCI 102 DLCI 201 DLCI 301 Fa0/0 172.16.2.0 /24 Fa0/0 172.16.3.0 /24 S0/0/0.3=192.168.3.101/24 192.168.2.102 S0/0/0.2=192.168.2.101/24
  • Chapter 2 126© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP over MPLS  Multi-Protocol Label Switching (MPLS) is an Internet Engineering Task Force (IETF) standard architecture that combines the advantages of Layer 3 routing with the benefits of Layer 2 switching.  A unique feature of MPLS is its capability to perform label stacking, in which multiple labels can be carried in a packet.  The top label, which is the last one in, is always processed first. • Label stacking enables multiple LSPs to be aggregated, thereby creating tunnels through multiple levels of an MPLS network.
  • Chapter 2 127© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP over Layer 3 MPLS VPNs R1(config)# interface FastEthernet0/0 R1(config-if)# ip address 192.168.1.2 255.255.255.252 R1(config-if)# exit R1(config)# router eigrp 100 R1(config-router)# network 172.16.1.0 0.0.0.255 R1(config-router)# network 192.168.1.0 R1(config-router)# R2(config)# interface FastEthernet0/0 R2(config-if)# ip address 192.168.2.2 255.255.255.252 R2(config-if)# exit R2(config)# router eigrp 100 R2(config-router)# network 172.17.2.0 0.0.0.255 R2(config-router)# network 192.168.2.0 R2(config-router)# EIGRP AS 100 Layer 3 MPLS VPN Backbone Fa0/0 PE1 .1 PE2 192.168.2.0/30 .2.2 192.168.1.0/30 .1 EIGRP AS 100 Fa0/0 172.16.1.0 /24 172.17.2.0 /24 R2R1
  • Chapter 2 128© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP over Layer 3 MPLS VPNs R1# show ip eigrp neighbors IP-EIGRP neighbors for process 100 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 0 192.168.1.1 Fe0/0 10 00:07:22 10 2280 0 5 R2# show ip eigrp neighbors IP-EIGRP neighbors for process 100 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 0 192.168.2.1 Fe0/0 10 00:17:02 10 1380 0 5 EIGRP AS 100 Layer 3 MPLS VPN Backbone Fa0/0 PE1 .1 PE2 192.168.2.0/30 .2.2 192.168.1.0/30 .1 EIGRP AS 100 Fa0/0 172.16.1.0 /24 172.17.2.0 /24 R2R1
  • Chapter 2 129© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP over Layer 2 MPLS VPNs R1(config)# interface FastEthernet0/0 R1(config-if)# ip address 192.168.1.101 255.255.255.224 R1(config-if)# exit R1(config)# router eigrp 100 R1(config-router)# network 172.16.1.0 0.0.0.255 R1(config-router)# network 192.168.1.0 R1(config-router)# R2(config)# interface FastEthernet0/0 R2(config-if)# ip address 192.168.1.102 255.255.255.224 R2(config-if)# exit R2(config)# router eigrp 100 R2(config-router)# network 172.17.2.0 0.0.0.255 R2(config-router)# network 192.168.1.0 R2(config-router)# EIGRP AS 100 Layer 2 MPLS VPN Backbone Fa0/0 PE1 PE2 192.168.1.0/27 .102.101 192.168.1.0/27 EIGRP AS 100 Fa0/0 172.16.1.0 /24 172.17.2.0 /24 R2R1
  • Chapter 2 130© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP over Layer 2 MPLS VPNs R1# show ip eigrp neighbors IP-EIGRP neighbors for process 100 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 0 192.168.1.102 Fe0/0 10 00:07:22 10 2280 0 5 R2# show ip eigrp neighbors IP-EIGRP neighbors for process 100 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 0 192.168.1.101 Fe0/0 10 00:17:02 10 1380 0 5 EIGRP AS 100 Layer 2 MPLS VPN Backbone Fa0/0 PE1 PE2 192.168.1.0/27 .102.101 192.168.1.0/27 EIGRP AS 100 Fa0/0 172.16.1.0 /24 172.17.2.0 /24 R2R1
  • Chapter 2 131© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Load Balancing  Routes with a metric equal to the minimum metric are installed in the routing table. • Referred to as “equal-cost load balancing”. • All IP routing protocols on Cisco routers can perform equal-cost load balancing.  The maximum-paths maximum-path command can be used to allow up to 6 equal-cost paths. • Default is 4. • Setting the maximum-path option to 1 disables load balancing.
  • Chapter 2 132© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Equal-Cost Load Balancing R1(config)# router eigrp 100 R1(config-router)# network 172.16.1.0 0.0.0.255 R1(config-router)# network 192.168.1.0 R1(config-router)# network 192.168.2.0 R1(config-router)# network 192.168.3.0 R1(config-router)# network 192.168.4.0 R1(config-router)# maximum–paths 3 R1(config-router)# R1 Topology Table Advertised Distance (AD) Network Neighbor AD FD 172.16.2.0/24 R2 20 40 R3 20 40 R4 20 40 R5 20 40
  • Chapter 2 133© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Unequal Cost Load Balancing  EIGRP can also balance traffic across multiple routes that have different metrics. • Referred to as unequal-cost load balancing.  The degree to which EIGRP performs load balancing is controlled 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 install multiple loop-free routes with unequal cost in the routing table. • EIGRP will always install successors (the best routes) in the routing table. • The variance allows feasible successors (and only feasible successor routes) as candidate routes to potentially be installed in the routing table.
  • Chapter 2 134© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Unequal-Cost Load Balancing R1(config)# router eigrp 100 R1(config-router)# variance 2 R1(config-router)# R1 Topology Table Advertised Distance (AD) Network Neighbor AD FD 172.16.2.0/24 R2 10 30 R3 10 20 R4 25 45 R5 10 50
  • Chapter 2 135© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Bandwidth Use Across WAN Links  EIGRP operates efficiently in WAN environments and is scalable on both point-to-point links and NBMA multipoint and point-to-point links.  However, default configuration of WAN connections may not be optimal therefore a solid understanding of EIGRP operation coupled with knowledge of link speeds can yield an efficient, reliable, scalable router configuration.  There are two commands which could be configured to improve EIGRP operation: • bandwidth • ip percent-bandwidth
  • Chapter 2 136© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Setting EIGRP Bandwidth on a WAN  EIGRP assumes the default bandwidth on the link instead of the true bandwidth, therefore suboptimal path selection may result. • For example, Serial links commonly default to 1.5 Mbps however the actual CIR may be 128 Kbps. • DUAL would use the 1.5 Mbps value instead of the actual slower 128 Kbps value in its metric calculation.  It is recommended to configure the bandwidth setting using the bandwidth kilobits on serial interfaces.  An important WAN consideration is the fact that multipoint interfaces physical bandwidth setting is shared equally by all neighbors. • EIGRP uses the bandwidth setting of the physical interface divided by the number of Frame Relay neighbors connected on that physical interface to get the bandwidth attributed to each neighbor. • The EIGRP configuration should reflect the correct percentage of the actual available bandwidth on the line.
  • Chapter 2 137© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP WAN Configuration – Example #1  All VCs share the bandwidth evenly: 4 (VC) x 56 (CIR) = 224 CIR 56 R1 EIGRP AS 100 Frame Relay R3 R4 R2 R5 CIR 56 CIR 56 CIR 56 T1 (1.5 Mbps) S0/0/0 R1(config)# interface S0/0/0 R1(config-if)# encapsulation frame-relay R1(config-if)# bandwidth 224
  • Chapter 2 138© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP WAN Configuration – Example #2a  R2, R3, and R4 share the same CIR. To protect against overwhelming the slowest-speed circuit (to R5) the bandwidth should be configured to the lowest CIR multiplied by the number of circuits. 4 (VC) x 56 (CIR) = 224 R1(config)# interface S0/0/0 R1(config-if)# encapsulation frame-relay R1(config-if)# bandwidth 224 R1 EIGRP AS 100 Frame Relay R3 R4 R2 R5 T1 (1.5 Mbps) S0/0/0 CIR 256 BW 224 CIR 256 BW 224 CIR 256 BW 224 CIR 56 BW 56
  • Chapter 2 139© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP WAN Configuration – Example #2b  An alternate solution is to configure a multipoint subinterface for routers R2, R3, and R4 and configure a point-to-point subinterface network for R5. R1 EIGRP AS 100 Frame Relay R3 R4 R2 R5 T1 (1.5 Mbps) S0/0/0 CIR 256 BW 224 CIR 256 BW 224 CIR 256 BW 224 CIR 56 BW 56 R1(config)# interface S0/0/0 R1(config-if)# encapsulation frame-relay R1(config-if)# interface S0/0/0/0.1 multipoint R1(config-subif)# bandwidth 768 R1(config-subif)# exit R1(config)# interface S0/0/0/0.2 point-to-point R1(config-subif)# bandwidth 56 R1(config-subif)#
  • Chapter 2 140© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP ip bandwith-percent  By default, EIGRP is set to use up to 50% of the bandwidth of an interface to exchange routing information.  The ip bandwidth-percent eigrp command can be configured to control the amount of bandwidth available to EIGRP. • This is not the same as the bandwidth command. • However, this command relies on the value set by the bandwidth command.
  • Chapter 2 141© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public ip 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 the configured bandwidth that EIGRP can use.  The percentage value can be set to greater than 100.
  • Chapter 2 142© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Configuring and Verifying EIGRP Authentication
  • Chapter 2 143© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Router Authentication  Many routing protocols support authentication such that a router authenticates the source of each routing update packet that it receives.  Simple password authentication is supported by: • IS-IS • OSPF • RIPv2  MD5 authentication is supported by: • OSPF • RIPv2 • BGP • EIGRP
  • Chapter 2 144© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Simple 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 message digest, or hash, of the key, key-id and message. • Message digest is sent with packet; key is not sent. • Is secure.
  • Chapter 2 145© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP MD5 Authentication  EIGRP supports MD5 authentication.  Router generates and checks every EIGRP packet. Router authenticates the source of each routing update packet that it receives.  Configure a “key” (password) and key-id; each participating neighbor must have same key configured.
  • Chapter 2 146© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public MD5 Authentication EIGRP MD5 authentication: • Router generates a message digest, or hash, of the key, key-id, and message. • 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 2 147© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Planning for EIGRP  The following key parameters must be defined in enough detail 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 2 148© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Configure 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 2 149© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Configure 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-id Router(config-keychain-key)# key-string text  Identify key string (password)
  • Chapter 2 150© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Configure 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 2 151© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Enable 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-system name-of-chain
  • Chapter 2 152© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Configuring EIGRP MD5 Authentication Fa0/0Fa0/0 R1 R2 172.16.1.0 /24 EIGRP AS 100 R1# show running-config ! <output omitted> ! key chain R1chain key 1 key-string FIRST-KEY accept-lifetime 04:00:00 Jan 1 2009 infinite send-lifetime 04:00:00 Jan 1 2009 04:00:00 Jan 31 2009 key 2 key-string SECOND-KEY accept-lifetime 04:00:00 Jan 25 2009 infinite send-lifetime 04:00:00 Jan 25 2009 infinite ! <output omitted> ! interface FastEthernet0/0 ip address 172.16.1.1 255.255.255.0 ! interface Serial0/0/0 bandwidth 64 ip address 192.168.1.101 255.255.255.224 ip authentication mode eigrp 100 md5 ip authentication key-chain eigrp 100 R1chain ! router eigrp 100 network 172.16.1.0 0.0.0.255 network 192.168.1.0 auto-summary 172.17.2.0 /24 S0/0/0 S0/0/0 64 kbps 192.168.1.96 /27 .101 .102 .1.1
  • Chapter 2 153© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Configuring EIGRP MD5 Authentication Fa0/0Fa0/0 R1 R2 172.16.1.0 /24 EIGRP AS 100 R2# show running-config ! <output omitted> ! key chain R2chain key 1 key-string FIRST-KEY accept-lifetime 04:00:00 Jan 1 2009 infinite send-lifetime 04:00:00 Jan 1 2009 infinite key 2 key-string SECOND-KEY accept-lifetime 04:00:00 Jan 25 2009 infinite send-lifetime 04:00:00 Jan 25 2009 infinite ! <output omitted> ! interface FastEthernet0/0 ip address 172.17.2.2 255.255.255.0 ! interface Serial0/0/0 bandwidth 64 ip address 192.168.1.102 255.255.255.224 ip authentication mode eigrp 100 md5 ip authentication key-chain eigrp 100 R2chain ! router eigrp 100 network 172.17.2.0 0.0.0.255 network 192.168.1.0 auto-summary 172.17.2.0 /24 S0/0/0 S0/0/0 64 kbps 192.168.1.96 /27 .101 .102 .1.1
  • Chapter 2 154© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Verifying MD5 Authentication R1# *Apr 21 16:23:30.517: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 192.168.1.102 (Serial0/0/0) is up: new adjacency R1# R1# show ip eigrp neighbors IP-EIGRP neighbors for process 100 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 0 192.168.1.102 Se0/0/0 12 00:03:10 17 2280 0 14 R1# R1# show ip route <output omitted> Gateway of last resort is not set D 172.17.0.0/16 [90/40514560] via 192.168.1.102, 00:02:22, Serial0/0/0 172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks D 172.16.0.0/16 is a summary, 00:31:31, Null0 C 172.16.1.0/24 is directly connected, FastEthernet0/0 192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks C 192.168.1.96/27 is directly connected, Serial0/0/0 D 192.168.1.0/24 is a summary, 00:31:31, Null0 R1# R1# ping 172.17.2.2 Type 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 2 155© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Verifying MD5 Authentication R1# show key chain Key-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 2 156© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Troubleshooting MD5 Authentication R1# debug eigrp packets EIGRP 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/rely 0/0 R2# debug eigrp packets EIGRP 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/rely 0/0
  • Chapter 2 157© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Configuring EIGRP MD5 Authentication Fa0/0Fa0/0 R1 R2 172.16.1.0 /24 EIGRP AS 100 R1(config-if)# key chain R1chain R1(config-keychain)# key 2 R1(config-keychain-key)# key-string wrongkey R1(config-keychain-key)# 172.17.2.0 /24 S0/0/0 S0/0/0 64 kbps 192.168.1.96 /27 .101 .102 .1.1 R2# debug eigrp packets EIGRP 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 (invalid authentication) *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 failure R2# R2# show ip eigrp neighbors IP-EIGRP neighbors for process 100 R2#
  • Chapter 2 158© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Optimizing EIGRP Implementations
  • Chapter 2 159© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Factors 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 topology change occurs.  Depth of topology: the number of hops that information must travel to reach all routers.  Number of alternate paths through the network.
  • Chapter 2 160© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Query Process  Queries are sent when a route is lost and no feasible successor is available.  The lost route is now in “active” state.  Queries are sent to all neighboring routers on all interfaces except 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; this stops the query from spreading in that branch of the network.
  • Chapter 2 161© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Overwhelming EIGRP Query Process  In a large internetwork EIGRP queries can generate many resources.  Several solutions exist to optimize the query propagation process and to limit the amount of unnecessary EIGRP load on the links, including: • Summarization • Redistribution • EIGRP stub routing feature.
  • Chapter 2 162© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Stuck-in-Active  If a router does not receive a reply to all the outstanding queries within default 3 minutes (180 seconds), the route goes 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 summarization and the ip summary-address eigrp command. • Configure the remote routers as stub EIGRP routers.
  • Chapter 2 163© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public SIA Solution: Summarization  Poorly designed networks can make summarization difficult.  Manually summarize the routes whenever possible to support a hierarchical network design.  The more networks EIGRP summarizes, the lower the number of queries being sent out. • Ultimately reduces the occurrence of SIA errors.
  • Chapter 2 164© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public SIA Solution: Summarization  This network design is better because subnet addresses from individual major networks are localized within each cloud, allowing summary routes configured using the ip summary-address eigrp command to be injected into the core.  As an added benefit, the summary routes act as a boundary for the queries generated by a topology change.
  • Chapter 2 165© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public SIA Solution: Stub Networks  The EIGRP Stub Routing feature: • Improves network stability • Reduces resource utilization and • Simplifies remote router (spoke) configuration
  • Chapter 2 166© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Stub Routing  Stub routing is commonly used in hub-and-spoke topology.  Stub router sends a special peer information packet to all neighboring routers to report its status as a stub router. • Any neighbor that receives a packet informing it of the stub status does not query the stub router for any routes. • Stub routers are not queried and instead, hub routers connected to the stub router answer the query on behalf of the stub router.  Only the remote routers are configured as stubs.
  • Chapter 2 167© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public EIGRP Stub  Configure a router as a stub router. Router(config-router)# eigrp stub [receive-only | connected | static | summary | redistributed] Parameter Description receive-only Restricts the router from sharing any of its routes with any other router within an EIGRP AS. Keyword cannot be combined with any other keyword. connected Permits the EIGRP stub routing feature to send connected routes. This option is enabled by default and is the most widely practical stub option. static Permits the EIGRP stub routing feature to send static routes. Redistributing static routes with the redistribute static command is still necessary. summary Permits the EIGRP stub routing feature to send automatically summarized and / or manually summarized routes. This option is enabled by default. redistributed Permits the EIGRP stub routing feature to send redistributed routes. Redistributing routes with the redistribute command is still necessary.
  • Chapter 2 168© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Example: EIGRP Stub Parameters  If stub connected is configured: • 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 is configured: • 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 2 169© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Example: EIGRP Stub Parameters (Cont.)  If stub static is configured: • 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 is configured: • B won’t advertise anything to A, so A needs to have a static route to the networks behind B to reach them.
  • Chapter 2 170© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Graceful Shutdown
  • Chapter 2 171© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public Resources  http://www.cisco.com/go/eigrp  http://www.cisco.com/en/US/customer/docs/ios/iproute_eigr p/command/reference/ire_book.html
  • Chapter 2 172© 2007 – 2010, Cisco Systems, Inc. All rights reserved. Cisco Public  Lab 2-1 EIGRP Configuration, Bandwidth, and Adjacencies  Lab 2-2 EIGRP Load Balancing  Lab 2-3 EIGRP Summarization and Default Network Advertisement  Lab 2-4 EIGRP Frame Relay Hub-and-Spoke: Router Used as a Frame Relay Switch  Lab 2-5 EIGRP Authentication and Timers  Lab 2-6 EIGRP Challenge Lab  Lab 2-7 Troubleshooting EIGRP Chapter 2 Labs