The document provides an overview of basic network and routing concepts. It describes enterprise network infrastructure with campus and edge components. It discusses the roles of dynamic routing protocols in exchanging network reachability information. Interior gateway protocols are used within an organization while exterior protocols exchange routes between autonomous systems. Common routing protocols include distance vector, link-state, and protocols can be divided into interior and exterior groups. The document also covers concepts like convergence, route summarization, scalability, network technologies, and routing protocol configurations over different networks.

1. Implementing Cisco
IP Routing (ROUTE)
Foundation Learning Guide
CCNP ROUTE 300-101
Basic Network and Routing Concepts
Chapter 1

2. Basic Network and Routing Concepts
• An overview of routing protocols that focuses on
characteristics that describe their differences.
• Describe how limitations of different underlying technologies
affect routing protocols.
• Closer look at how Layer 2 and Layer 3 VPNs affect routing
protocols.
• Dynamic Multipoint Virtual Private Network (DMVPN) is
introduced as a scalable VPN solution
• Configuration of a simple routing protocol RIPng, which
supports Internet Protocol version 6 (IPv6).

3. Differentiating Routing Protocols
Upon completing this section, you will be able to:
•Identify general enterprise network infrastructure
•Describe the role of dynamic routing protocols within the
enterprise network infrastructure
•Identify the major areas of differencesmajor areas of differences among routing protocols
•Describe the differences between IGP and EGP routing
protocols
•Describe the different types of routing protocols
•Identify the importance of convergence
•Describe route summarization
•Describe what influences routing protocol scalability

4. Enterprise Network Infrastructure
• Network infrastructure of enterprises today can be
complicated at first glance.
• A large number of interconnected devices and differences
between physical and logical topologies are just two reasons
for this complexity.
• Devices can be mapped into different areasDevices can be mapped into different areas according to the
functionality that they provide in the network infrastructure

5. Figure 1-1 Enterprise Network Infrastructure
Enterprise Campus provides access to the network communications services and resources to end usersprovides access to the network communications services and resources to end users
and devicesand devices. Single geographic location, designed using a hierarchical model: Access, Distribution and
Core layers
Enterprise edge provides remote sites with access to the same network services as users at the main site,provides remote sites with access to the same network services as users at the main site,
aggregates private WAN linksaggregates private WAN links, VPN connections & Internet connectivity

7. Figure 1-2 Role of Dynamic Routing Protocols
The basic objective of routing protocols is to exchangeexchange network reachability informationnetwork reachability information
between routers and dynamically adaptdynamically adapt to network changes.

8. Figure 1-3 IGP versus EGP
Interior Gateway Protocols (IGP): used within the organization, and they exchange the routes within anexchange the routes within an
AAS
Exterior Gateway Protocols (EGP): exchanging routes between different autonomous systemsexchanging routes between different autonomous systems. Border
Gateway Protocol (BGP)

9. Routing protocols can be divided into the following groups:
•Distance vector protocols Determines the:
• Direction (vector, Next hop or Exit interface)
• Distance (such as link cost or number of hops) to any link in the
network.
• Distance vector protocols use routers as signposts along the
path to the final destination. Uses Bellman-Ford algorithm
•Link-state protocols: The link-state approach uses the Shortest Path First
(SPF) algorithm to create an abstract of the exact topology of the
entire network or at least within its area. A link-state routing
protocol is like having a complete map of the network topology.

10. Convergence describes the process of when routers notice change in the
network, exchange the information about the change, and perform necessary
calculations to reevaluate the best routes.
A converged network describes the state of the network in which allall
routers have the same view on the network topologyrouters have the same view on the network topology.
Convergence time describes how fast network devices can reach the state ofhow fast network devices can reach the state of
convergence after a topology change.convergence after a topology change.
Convergence time affected by:
Routing protocol timers
Route summarization

11. • Route summarization enables you to reduce routing overhead and improve
stability and scalability of routing by reducing the amount of routingreducing the amount of routing
information that is maintained and exchanged between routersinformation that is maintained and exchanged between routers.
• The purpose of route summarization is to squeeze several subnets into onesqueeze several subnets into one
aggregate entry that describes all of themaggregate entry that describes all of them. As shown in Figure 1-5 , route
summarization reduces the size of routing tables
• Different routing protocols support different route summarization options.
• IP addresses must be hierarchically assigned in contiguous blocks across
the network.

12. Route Protocol Scalability
•As a network grows and becomes larger, the risk of routing protocol
instability or long convergence times becomes greaterinstability or long convergence times becomes greater.
•Scalability describes the ability of a routing protocol to support
further network growth.
Scalability factors include:
•Number of routes
•Number of adjacent neighbors
•Number of routers in the network
•Network design
•Frequency of changes
•Available resources (CPU and memory)
OSPF supports the use of hierarchical areas that divide one large network intodivide one large network into
several subdomainsseveral subdomains.
EIGRP supports the configuration of stub routers to optimize
information exchange process and improve scalability.

13. Understanding Network Technologies
You can establish routing protocols over a variety of different networkestablish routing protocols over a variety of different network
technologiestechnologies.
It is important to consider the limitations of a specific solutionconsider the limitations of a specific solution and how it
affects routing protocol deployments and operation.
Upon completing this section, you will be able to:
•Differentiate traffic types
•Differentiate IPv6 address types
•Describe ICMPv6 neighbor discovery
•Differentiate network types
•Describe the impact of NBMA (Non-broadcast Multiaccess) on routing
protocols
•Describe how the Internet breaks enterprise routing

14. Traffic types:
•Unicast: Unicast addresses are used in a one-to-one contextused in a one-to-one context. Unicast traffic is exchangedexchanged
only between one sender and one receiveronly between one sender and one receiver.
•Multicast: Multicast addresses identify a group of interfaces across different devicesaddresses identify a group of interfaces across different devices.
Traffic that is sent to multiple destinations at the same time.
• IPv4 multicast addresses is 224.0.0.0–239.255.255.255.
• IPv6 reserved multicast addresses have the prefix FF00::/8.
•Anycast: IPv6 anycast address is assigned to an interface on more than one nodeassigned to an interface on more than one node. Packet
is routed to the nearest interface that has this address.
• A common use case for anycast is the Internet DNS server.
•Broadcast: IPv4 broadcast addresses are used when sending traffic to all devices in the
subnet. IPv6 does not use a broadcast addressIPv6 does not use a broadcast address
• Local broadcast address 255.255.255.255.
• Directed broadcast address N.N.N.255

15. Traffic Types
•Early routing protocols used only broadcasts to exchange routing
information.
•All modern IGPs use multicast addresses to perform neighbor discovery,
exchange routing information, and send updates.

16. IPv6 Address Types
There are several different basic types of IPv6 addresses. It is important that you
are familiar with them, since some of them are also used by routing protocols.
RFC 3587 specifies 2000::/3 to be global unicast address space that the IANA may
allocate to the Regional Internet Registries (RIRs).

17.  The following displays how IPv6 global unicast addresses
are allocated by the IANA.
• Only a small portion (12.5%) of the IPv6 address space is being
allocated to the Registries in the range of 2001::/16.
IPv6 Global Unicast Address

18. IPv6 Global Unicast Address
• The global unicast address typically consists of:
• A 48-bit global routing prefix
• A 16-bit subnet ID
• A 64-bit interface ID (typically in EUI-64 bit format discussed later).
Global Routing Prefix
Subnet
ID Interface ID
2001
0010
0008 21B:D5FF:FE5B:A408
/23
Registry
/32
ISP Prefix
/48
Site Prefix
/64
Subnet Prefix

19. Network Types
Not all Layer 2 network topologies support all traffic types. Because unsupported traffic
types influence the operation of routing protocols, it is important to be aware of the
limitations of specific network topologies.
Point-to-point network: A network that
connects a single pair of routers.
A serial link is an example of a point-to-point
connection.
Broadcast network: A network that can
connect many routers along with the
capability to address a single message to all of
the attached routers. Ethernet is an
example of a broadcast network.
Non-broadcast Multiaccess (NBMA)
network: A network that can support many
routers but does not have broadcast
capability. (ex: Frame Relay)
The sender needs to create an individual copy of the same packet for each recipient if it
wishes to inform all connected neighbors.

20. Frame Relay NBMA Operation
Frame Relay Star Topologies
Star Topology (Hub and Spoke)
The simplest WAN topology is a star. In this topology, SPAN Engineering
Company has a central site in Chicago that acts as a hub and hosts the primary
services.

21. Frame Relay Operation
Frame Relay Mesh Topologies
Using Frame Relay Mesh, a network designer can build multiple connectionsbuild multiple connections
simply by configuring additional VCs on each existing physical linksimply by configuring additional VCs on each existing physical link.
This software upgrade grows the star topology to a full mesh topology
without the expense of additional hardware or dedicated lines.

22. Split horizon: For distance vector routing protocols, the split-horizon rule reduces
routing loops. As illustrated in Figure 1-9, it prevents a routing update that is received
on an interface from being forwarded out of the same interface.
The hub router receives the update on its physical interface but cannot
forward it through the same interface to other spoke routers.
Split horizon is not a problem if there is a single PVC on a physical interface because
this type of connection would be point-to-point.
If you use a single Frame Relay, multipoint interfacesingle Frame Relay, multipoint interface to interconnect multiple sites,
reachability issues may be a problemreachability issues may be a problem because of the NBMA nature of Frame Relay.
The Frame Relay NBMA topology can cause the following issues:
NBMA Networks

23. Neighbor discovery:
OSPF over NBMA networks works in a nonbroadcast network mode by
default, and neighbors are not automatically discovered. You can statically
configure neighbors, but an additional configuration is required to manually
configure the hub as a Designated Router (DR).
OSPF treats an NBMA network like Ethernet by default, and on Ethernet, a DR is
needed to exchange routing information between all routers on a segment. Therefore,
only the hub router can act as a DR because it is the only router that has PVCs with
all other routers.

24. Broadcast replication:
For multipoint connections over a single interface that terminates at multiple
PVCs, the router must replicate broadcast packets, such as routingsuch as routing
update broadcastsupdate broadcasts, on each PVC to the remote routerson each PVC to the remote routers.
These replicated broadcast packets consume bandwidth and cause significant
latency variations in user traffic.

25. Subinterfaces:
Subinterfaces overcome some limitations of NBMA networks.
You can choose between two different types of subinterfacestwo different types of subinterfaces:
•Point-to-point subinterfaces: Each subinterface, which provides
connectivity between two routers, uses its own subnet for addressing.
Connectivity looks just like several physical point-to-point links, no issues with
neighbor discovery and the split-horizon rule.
•Point-to-multipoint subinterfaces: One subnet is shared between all virtual
circuits. Because private address space is normally used for addressing, saving
address space is not a significant benefit.
Point-to-point subinterfaces are the preferred and recommended choice.

26. Figure 1-11 Configuring Static Routing
Routing Over the Internet
Principles of Static Routing
A static route can be used in the following circumstances:
•When it is undesirable to have dynamic routing updates forwarded across slow
bandwidth links, such as a dialup link.
•When the administrator needs total control over the routes used by the router.
•When a backup to a dynamically recognized route is necessary.
•When it is necessary to reach a network accessible by only one path (a stub
network).
•When a router connects to its ISP and needs to have only a default route
pointing toward the ISP router, rather than learning many routes from the ISP.
•When a router is underpowered and does not have the CPU or memory resources
necessary to handle a dynamic routing protocol.

27. Configuring a Static Default Route
•In some circumstances, a router does not need to recognize the details of remote
networks.
•The router is configured to send all traffic in a particular direction; this is known
as a default route.
•To create a static default route, use the normal ip route command, but with the
destination network and its subnet mask both set to 0.0.0.0.
• In Figure 1-12 , to reach the 172.16.1.0/24 network, Router B still needs a static
route pointing out its S0/0/0 interface.
• Entering the show ip route command on Router A in Figure 1-12 returns the
information shown in Example 1-1 .

28. Basic PPP Overview
•Point-to-Point Protocol (PPP) has several advantages over its predecessor High-Level
Data Link Control (HDLC).
The following example enables PPP encapsulation on interface serial 0/0/0:
R1# configure terminal
R1(config)# interface serial 0/0/0
R1(config-if)# encapsulation ppp
PPP Authentication Overview
RFC 1334 defines two protocols for authentication, PAP and CHAP.
•PAP is a very basic two-way process, there is no encryption. The username and
password are sent in plaintext.
•CHAP authentication sends a challenge to the remote device.
•The remote device must encrypt the challenge value with a shared secret and return
the encrypted value and its name to the local router in a response message.
•LCP (Link Control Protocol) establishes the link & chooses the authentication protocol.

29. PPPoE
•PPP can be used on all serial links including those links created with older dialup
analog and ISDN modems.
•In addition, ISPs often use PPP as the data-link protocol over broadband
connections like DSL.
•With PPP enabled, ISPs can use PPP to assign each customer one public IPv4
address.
•During the CHAP to authenticate customers ,ISPs can check accounting records.
Ethernet links do not natively support PPP.
A solution to this problem was created: PPP over Ethernet (PPPoE).
•PPPoE allows the sending of PPP frames encapsulated inside Ethernet frames.
•The modem converts the Ethernet frames to PPP frames by stripping the Ethernet
headers.
•The modem then transmits the PPP frames on the ISP’s DSL network.
•ISP could continue to use the same authentication model as with analog and ISDN.
To create a PPP tunnel, the configuration uses a dialer interface.
•The PPP configuration is placed on the dialer interface, not on the physical interface.
•The PPP CHAP configuration usually defines one-way authentication.
•The physical Ethernet interface then enabled with the command pppoe enable
•The maximum transmission unit (MTU) should be reduced to 1492, versus the
default of 1500, to accommodate the PPPoE headers.

30. • Frame Relay is a switched WAN technology where virtual circuits (VCs) are
created by a service provider (SP) through the network.
• VCs provide a bidirectional communication path from one device to another.
• VCs are identified by DLCIs
• DLCI values typically are assigned by the Frame Relay service provider
• Frame Relay allows multiple logical VCs to be multiplexed over a single physical
interface.
• Frame Relay is statistically multiplexed, meaning that it transmits only one frame at
a time, but that many logical connections can co-exist on a single physical line.

31. Star Topology (Hub and Spoke)
The simplest WAN topology is a star. In
this topology, SPAN Engineering Company
has a central site in Chicago that acts as a
hub and hosts the primary services.
Using Frame Relay Mesh, a network
designer can build multiple
connections simply by configuring
additional VCs on each existing link
This software upgrade grows
the star topology to a full
mesh topology without the
expense of additional
hardware or dedicated lines.

32. Figure 1-16 EIGRP on a Physical Frame Relay Interface
• Split horizon is disabled by default on Frame Relay physical interfaces.
• Therefore, routes from Router R2 can be sent to Router R3, and vice versa.
• Note that Inverse ARP does not provide dynamic mapping for the communication
between Routers R2 and R3 because they are not connected with a PVC.
• You must configure this mapping manually.
192.168.1.101 255.255.255.0
192.168.1.102 102 broadcast

33. MPLS
•MPLS (Multiprotocol Label Switching) is a transport mechanism that is developed to
carry data over the packet-switched network.
•Designed to offer a great level of flexibility to operate seamlessly with any Layer 3 or
Layer 2 technology.
•VPN service enables service providers and large enterprises to build flexible, scalable,
and secure VPNs.
• MPLS is a switching mechanism.
• A 32 bit header (label) is inserted by the provider (PE) router.
• Packets are switched through the MPLS network.
• The label is removed by the PE at the other end of the MPLS network.
• To the customer, it looks like a Layer 2 or Layer 3 connection.

34. Figure 1-17 Layer 3 MPLS VPN Solutions
Two types of MPLS VPNs have been developed:
1. The Layer 2 MPLS VPN backbone
solution is providing the Layer 2 service
across the
backbone, R1 and R2 are connected together
directly using the same IP subnet. If you
deploy a routing protocol over the Layer 2
MPLS VPN, neighbor adjacency is established
between your R1 and R2 routers. The figure
presents the connectivity through the
backbone.
2. The Layer 3 MPLS VPN backbone solution is
providing the Layer 3 service across the
backbone, R1 and R2 are connected to ISP edge
routers. A separate IP subnet is used on each side.
If you deploy a routing protocol over this VPN,routing protocol over this VPN,
service providers need to participate in itservice providers need to participate in it. Neighbor
adjacency is established between your R1 and theR1 and the
closest PE router and between your R2 and it’sclosest PE router and between your R2 and it’s
closest PE router.closest PE router.

35. A GRE tunnel (Generic Routing Encapsulation) a point-to-point tunnel developed by Ciscopoint-to-point tunnel developed by Cisco
that allows a wide variety of passenger protocols to be transported over the IP network.
It comprises three main components:
1.A passenger protocol or encapsulated protocol, such as IPv4 or IPv6 that is beingthat is being
encapsulated.encapsulated.
2.A carrier protocol, GRE in this example, that is defined by Cisco as a multiprotocol
carrier protocol and described in RFC 2784.
3.A transport protocol, such as IP, that carries the encapsulated protocolcarries the encapsulated protocol.
GRE has the following characteristics:
•GRE uses a protocol-type field in the GRE header to support the encapsulation of any
OSI Layer 3 protocol (IPv4, IPv6, IPX, AppleTalk).
•GRE itself is stateless. It does not include any flow-control mechanisms, by default.
•GRE does not include any strong security mechanisms to protect its payload.
•The GRE header, along with the tunneling IP header, creates at least 24 bytes of
additional overhead for tunneled packets.

36. With a generic hub-and-spoke topology, youyou
can typically implement static tunnelscan typically implement static tunnels
(typically GRE with IPsec) between central
hub and remote spokes, as shown in Figure
Dynamic Multipoint Virtual Private Network:
The main characteristics of the mGRE configuration are as follows:
•OnlyOnly one tunnel interface needs to be configured on a router to supportone tunnel interface needs to be configured on a router to support
multiple remote GRE peersmultiple remote GRE peers. In a hub-and-spoke network, a single mGREa single mGRE
tunnel interface on the hub accommodates many spoke GRE peerstunnel interface on the hub accommodates many spoke GRE peers.
•In order to learn about the IP addresses of other peer, devices using mGRE
require NHRP to build dynamic GRE tunnels. Peers can also use dynamically
assigned addresses that will then be used by NHRP when registering with the
hub. (NHRP - Next Hop Resolution Protocol)
•mGRE interfaces also support unicast, multicast, and broadcast traffic.

37. Multipoint GRE
An important characteristic of the DMVPN solution is scalabilityDMVPN solution is scalability, which is enabled by
deploying Multipoint GRE (mGRE). mGRE technology enables a single GRE interfacesingle GRE interface
to support multiple GRE tunnelsto support multiple GRE tunnels and simplifies the complexity of the configuration.
Figure 1-20 shows two options for implementing mGRE functionality:
•The left diagram shows the hub that is optimized with an mGRE interface. In this
setup, only a single interface is required on the hub. However, you must deploy NHRPmust deploy NHRP
for the hub to learn spoke addressesfor the hub to learn spoke addresses and correctly provision the spoke-to-hub GRE
tunnels.
•In the right diagram, all devices in a hub-and-spoke network use the mGRE interface.
Using NHRP, these devices can establish a partial mesh or full mesh of GRE tunnels. By
only configuring a single mGRE interface on each device, the configuration is greatlyconfiguration is greatly
simplified and manageability improved.simplified and manageability improved.

38. • NHRP is a client-server protocol, the hub acts as the server, and the spokes are clients.
• NHRP is used by routers to determine the IP address of the next hop in IP tunneling networks.
• NHRP creates a mapping for a tunnel IP address to the physical interface IP address for each
spoke at the hub.
Client-Server Protocol

39. Authentication
• Ensures that a message:
• Comes from an authentic source and
• Goes to an authentic destination
Data confidentiality
• Protecting data from eavesdroppers (encryption)
• Aims at protecting the message contents from being intercepted by unauthenticated or
unauthorized sources.
Data integrity
• Across the Internet, there is always the possibility that the data has been modified.
Antireplay protection:
• Antireplay protection verifies that each packet is unique and not duplicated.
• VPN with IPsec supports
• IP unicast only
• IPsec with GRE supports
• IP multicast
• dynamic IGP routing protocols
• non-IP protocols
• IPsec has two encryption modes:
• Tunnel mode
• Transport mode
Secure VPN

40.  IPsec is best thought of as a set of features that protects IP data
as it travels from one location to another.
 IPsec can protect only the IP layer and up (transport layer and
userdata).
 IPsec cannot extend its services to the data link layer.
 If protection of the data link layer is needed, then some form
of link encryption is needed.
 Encryption, Authentication and data integrity are NOT a
requirement of IPsec, they’re optional (although heavily
implemented) feature of IPsec.

41. IPsec
Security is also an important part of the DMVPN solution.
•Security services are enabled by the use of the IPsec framework.
•IPsec is a framework of open standards that define how to provide secure
communications.
•It relies on existing algorithms to implement the:
• Encryption
• Authentication
• key exchange.
IPsec provides four important security services:
•Confidentiality (encryption): The sender can encrypt the packets before
transmitting them across a network.
•Data integrity: The receiver can verify that the data was transmitted through
the path without being changed or altered in any way.
•Authentication: Authentication ensures that the connection is made with the
desired communication partner.
•Antireplay protection: Verifies that each packet is unique and not duplicated.
• IPsec packets are protected by comparing the sequence number of the
received packets with a sliding window on the destination host.

42. Routing and TCP/IP Operations
•Routing protocols are part of the TCP/IP protocol suite, specifically at Layer 3.
•Network communications requires a wide range of protocols responsible for a
wide variety of tasks to ensure communications between devices.
MSS (Maximum Segment Size) , Fragmentation, and PMTUD (Path MTU Discovery)
•Most transmission links enforce a small maximum packet length, 1500 Bytes, called
the maximum transmission unit (MTU).
•When a router receives an IPv4 packet larger than the MTUIPv4 packet larger than the MTU of the outgoing
interface, it must fragment the packet unless the DFmust fragment the packet unless the DF (Don’t Fragment) bit is set in the
IPv4 header.
Fragmentation causes several issues including the following:
•CPU and memory overhead in fragmentation of the packet
•CPU and memory overhead in destination devices during reassembly of packets
•Retransmission of the entire packet when one fragment is dropped
•Firewalls that do Layer 4 through Layer 7 filtering may have trouble processing
IPv4 fragments correctly
To avoid fragmentation of an IPv4 packet
•TCP MSS Sets the MTU of the outgoing interface minus 40 bytes.
•The 40 bytes take into account the 20-byte IPv4 header and 20-byte TCP header.
Example: a TCP MSS of 1460, which is 1500 bytes for the Ethernet MTU, minus 20
bytes for the IPv4 header, and minus 20 bytes for the TCP header.
MSS Maximum Size Segment

43. Path MTU Discovery (PMTUD) was developed for the purpose of determining the
lowest MTU along a path from the packet’s source to destination. PMTUD is only
supported by TCP.
PMTUD is performed by a host using the full MSS on the outgoing interface:
•When the TCP packets that exceeds the MTU cannot be fragmented; DF (Don’t
Fragment) bit is set.
•The router along the path will drop the packet and send an ICMP “Destination
Unreachable” message back to the originator of the packet.
•The ICMP Destination Unreachable message contains the code indicating
“fragmentation needed and DF set” and the packet was dropped.
•The source receives the ICMP message, reduces the size of the MSS to be within
the MTU, and retransmits the message.
*The PMTUD operations for IPv6 are similar to that of PMTUD for IPv4
TCP Starvation
TCP incorporates mechanisms for reliability, flow control, and congestion avoidance.
• TCP tries to do its part by backing off on bandwidth, called slow start .
UDP is faster and simpler data transmissions protocol, does not include these features.
• UDP without any flow control mechanisms continues, potentially using up the
available bandwidth given up by TCP.
This is known as TCP starvation/UDP dominance .

44. ICMP Redirect
ICMP Redirect messages are used by routers to notify the sender of a packet that
there is a better route available for a particular destination.
• R1 and R2, are connected to the same Ethernet segment as host PCA.
• The IPv4 default gateway of PCA is the IPv4 address of router R1.
• PCA sends a packet for PCX to its default gateway R1.
• R1 examines its routing table and determines the next hop as router R2, on the same
Ethernet segment as PCA.
• R1 forwards the packet out the same interface used to receive the packet from PCA.
• R1 also sends an ICMP Redirect message informing PCA of a better route to PCX by
way of R2.
The ICMPv6 Redirect message functions the same way as the Redirect message for
ICMPv4, with one additional feature. PCA can now send IPv6 packets directly to PCB
even though it is on a different IPv6 network.
Figure 1-23 ICMP Redirect

45. Implementing RIPng
•RIP is an IGP that is used in smaller networks.
•A distance vector routing protocol that uses hop count (15 Max) as a
routing metric.
•There are three versions of RIP: RIPv1 & RIPv2 (IPv4) ,and RIPng (IPv6).
Upon completing this section, you will be able to:
• Describe general RIP characteristics
• Describe how to configure and verify basic RIPng
• Describe how to configure RIPng to share default routes
• Analyze the RIPng database
As a routing loop-prevention technique, RIP implements:
•Split horizon, prevents routing information from being sent out the same
interface from which it was received.
•Split horizon with poison reverse is a similar technique but sends the
update with a metric of 16, which is considered unreachable by RIP.
•RIP is also capable of load balancing traffic over equal-cost paths. The
default is four equal-cost paths.

46. • RIP will choose the direct path—the one over the 100-Mbps link—
because the destination is only 2 hops away. The hop count over the
three 1-Gbps links is 4.
• In this case, RIP will choose the worse path.
• A more advanced protocol, such as OSPF or EIGRP, would not choose the
path over the weak, 100-Mbps link. Traffic would be forwarded over the
1-Gbps links.

48. • By default, RIPv2 automatically summarizes networks at major networkautomatically summarizes networks at major network boundariesboundaries,
summarizing routes to the classful network addressto the classful network address.
• To modify the default RIPv2 behavior of automatic summarization, use the
no auto-summary router configuration mode command:
Router(config-router)#Router(config-router)# no auto-summaryno auto-summary
The ip summary-address rip ip-address network-mask interface command is used to
summarize an address or subnet under a specific interface. AKA manual summarization
Router(config-if)# ip summary-address rip 102.0.0 255.255.0.0Router(config-if)# ip summary-address rip 102.0.0 255.255.0.0

49. There are two major differences between RIPv2 and RIPng:
•RIPv2 advertises routes for IPv4 and uses IPv4 for transport,
while RIPng advertises routes for IPv6 and uses IPv6 for
transport.
•The configuration of RIPng is quite different when
compared to RIPv2 configuration

50. Configuring RIPng
•We will begin by configuring basic RIPng on R2 using the topology in Figure 1-26 .
•RIPng is already preconfigured on R1.
•On R1, there is a static default route that is already configured, which routes all the
unknown traffic toward the Internet.
Basic RIPng Configuration
Next, IPv6 routing is enabled using the ipv6 unicast-routing command.
While IPv4 routing is enabled by default on Cisco routers, IPv6 routing is not.

51. Set the name of the process to “CCNP_RIP.”
The routing process name does not need to
match between neighbor routers. AS
RIPng process name has local significance
Enable RIPng on interfaces Ethernet 0/1 and Loopback0 with the:
ipv6 rip name enable interface subcommand, as shown in Example above .
•f IPv6 is not enabled on the interface and you are trying to enable this same
interface for RIPng, the ipv6 rip namename enable command will be rejected.
•If you forgot to create a routing processIf you forgot to create a routing process using the ipv6 router rip name command
and you enable RIPng on an interfaceenable RIPng on an interface, the command will be accepted. In this case,
the RIPng process will be automatically created by Cisco IOS SoftwareRIPng process will be automatically created by Cisco IOS Software.

52. IPv6 RIP summary-address Command
•The concept of classful networks doesn’t exist in IPv6, so there isn’t any
automatic route summarization in RIPng.
•To configure RIPng to advertise summarized IPv6 addresses on an
interface, manual summarization, use the:
ipv6 rip summary-address command in interface configuration
mode.
In the Example below , the two loopback interfaces on R1 are summarized
out the Ethernet 0/3 interface for the RIPng process CCNP_RIP.

53. Propagating a Default Route
In Figure 1-27 , R1 has a
configured static default route
that that sends all the
unknown traffic toward the
Internet.
There are two ways of sharing information about default routes through RIPng:
•The first way is specified through the originate keyword. In this case, R1 shares
the default route information alongside the information about every other route.
•The second way of sharing default route information is to use the only keyword.
With only , R1 will only share the default route with R2.

54. The show ipv6 rip next-hops output:
•Next hops are either the addresses of
IPv6 RIP neighbors from which you have
learned routes or explicit next hops that
are received in IPv6 RIP advertisements.
The show ipv6 rip database output:
•The RIP process
•The route prefix.
•The route metric
•Installed and expired, the keyword “installed”
means the route is in the routing table.
•Expires in, in which if the countdown timer
reaches 0, the route is removed from the routing
table and marked expired

55. Summary
In this chapter, you learned about differentiating routing protocols, various network
technologies, connecting remote locations to a central location and RIPng. The chapter focused
on the following topics:
•The role of static routes and dynamic routing protocols in enterprise networks.
•The differences between IGP and EGP routing protocols.
•The three types of routing protocols: distance vector, link-state and path vector.
•The importance of convergence time and how route summarization reduced convergence time
and improves scalability.
•The four traffic types: unicast, multicast, anycast, and broadcast.
•The differences between point-to-point, broadcast, and NBMA networks.
•How point-to-point subinterfaces are used to overcome the limitations of NBMA networks.
•How VPNs are used to provide security of a public Internet.
•Common types of VPNs: MPLS-based VPNs, GRE+IPsec, and DMVPN.
•How a customer establishes connectivity with a service provider using a routing protocol and a
layer 3 MPLS VPN.
•How static GRE tunnels can establish virtual point-to-point links and support dynamic routing
protocols.
•Using DMVPN to provide fully meshed VPN connectivity with a simple hub-and -spoke
configuration.
•How DMVPN relies on NHRP, mGRE, and IPsec.
•The differences and similarities between RIPv2 and RIPng.
•How to configure RIPng.
•How to propagate a default route in RIPng.