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Table Of Contents
Configuring Routing Information Protocol
Prerequisites for Configuring RIP
Restrictions for Configuring RIP
Information About Configuring RIP
RIP Version 2 and Enabling Authentication
Exchange of Routing Information
Interpacket Delay for RIP Updates
RIP Optimization over WAN Circuits
Neighbor Router Authentication
Enabling RIP and Configuring RIP Parameters
Specifying a RIP Version and Enabling Authentication
Enabling or Disabling Split Horizon
Disabling the Validation of Source IP Addresses
Configuring IP-RIP Delay Start for Routers Connected by a Frame Relay Network
Configuring Frame Relay on a Serial Subinterface
Configuration Examples for RIP
Address Family Timers: Example
IP-RIP Delay Start on a Frame Relay Interface: Examples
Feature Information for Configuring RIP
Configuring Routing Information Protocol
First Published: February 27, 2006Last Updated: July 30, 2010Routing Information Protocol (RIP) is a commonly used routing protocol in small to medium TCP/IP networks. It is a stable protocol that uses a distance-vector algorithm to calculate routes.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for Configuring RIP" section.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Contents
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Prerequisites for Configuring RIP
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Prerequisites for Configuring RIP
Before configuring RIP, the ip routing command is configured. For more information about configuring the ip routing command, see the Cisco IOS IP Routing: RIP Command Reference.
Restrictions for Configuring RIP
The metric that RIP uses to rate the value of different routes is hop count. The hop count is the number of routers that can be traversed in a route. A directly connected network has a metric of zero; an unreachable network has a metric of 16. This small range of metrics makes RIP an unsuitable routing protocol for large networks.
Information About Configuring RIP
To configure the Routing Information Protocol (RIP), you should understand the following concepts:
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RIP Overview
Routing Information Protocol uses broadcast User Datagram Protocol (UDP) data packets to exchange routing information. Cisco IOS software sends routing information updates every 30 seconds, which is termed advertising. If a router does not receive an update from another router for 180 seconds or more, it marks the routes served by the nonupdating router as being unusable. If there is still no update after 240 seconds, the router removes all routing table entries for the nonupdating router.
A router that is running RIP can receive a default network via an update from another router that is running RIP, or the router can source (generate) the default network itself with RIP. In both cases, the default network is advertised through RIP to other RIP neighbors.
The Cisco implementation of RIP Version 2 supports plain text and Message Digest 5 (MD5) authentication, route summarization, classless interdomain routing (CIDR), and variable-length subnet masks (VLSMs).
RIP Routing Updates
RIP sends routing-update messages at regular intervals and when the network topology changes. When a router receives a RIP routing update that includes changes to an entry, the router updates its routing table to reflect the new route. The metric value for the path is increased by 1, and the sender is indicated as the next hop. RIP routers maintain only the best route (the route with the lowest metric value) to a destination. After updating its routing table, the router immediately begins transmitting RIP routing updates to inform other network routers of the change. These updates are sent independently of the regularly scheduled updates that RIP routers send.
RIP Routing Metric
RIP uses a single routing metric (hop count) to measure the distance between the source and a destination network. Each hop in a path from source to destination is assigned a hop count value, which is typically 1. When a router receives a routing update that contains a new or changed destination network entry, the router adds 1 to the metric value indicated in the update and enters the network in the routing table. The IP address of the sender is used as the next hop. If the network of an interface network is not specified, it will not be advertised in any RIP update.
RIP Version 2 and Enabling Authentication
The Cisco implementation of RIP Version 2 supports authentication, key management, route summarization, CIDR, and VLSMs. For more information about managing authentication keys see the "Managing Authentication Keys" section of the "Configuring IP Routing Protocol-Independent Features" module.
By default, the software receives RIP Version 1 and Version 2 packets, but sends only Version 1 packets. You can configure the software to receive and send only Version 1 packets. Alternatively, you can configure the software to receive and send only Version 2 packets. To override the default behavior, you can configure which RIP version an interface sends. Similarly, you can also control how packets received from an interface are processed.
RIP Version 1 does not support authentication. If you are sending and receiving RIP Version 2 packets, you can enable RIP authentication on an interface.
The key chain determines the set of keys that can be used on the interface. If a key chain is not configured, no authentication is performed on that interface, not even the default authentication. Therefore, you must also perform the tasks in the section "Managing Authentication Keys" in the "Configuring IP Routing Protocol-Independent Features" module.
We support two modes of authentication on an interface for which RIP authentication is enabled: plain text authentication and MD5 authentication. The default authentication in every RIP Version 2 packet is plain text authentication.
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Exchange of Routing Information
RIP is normally a broadcast protocol, and in order for RIP routing updates to reach nonbroadcast networks, you must configure the Cisco IOS software to permit this exchange of routing information.
To control the set of interfaces with which you want to exchange routing updates, you can disable the sending of routing updates on specified interfaces by configuring the passive-interface router configuration command. See the discussion on filtering in the "Filter Routing Information" section in the "Configuring IP Routing Protocol-Independent Features" module.
An offset list is the mechanism for increasing incoming and outgoing metrics to routes learned via RIP. Optionally, you can limit the offset list with either an access list or an interface. To increase the value of routing metrics, use the following command in router configuration mode:
Routing protocols use several timers that determine such variables as the frequency of routing updates, the length of time before a route becomes invalid, and other parameters. You can adjust these timers to tune routing protocol performance to better suit your internetwork needs. You can make the following timer adjustments:
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It also is possible to tune the IP routing support in the software to enable faster convergence of the various IP routing algorithms, and, hence, quicker fallback to redundant routers. The total effect is to minimize disruptions to end users of the network in situations where quick recovery is essential
In addition, an address family can have explicitly specified timers that apply to that address-family (or VRF) only. The timers basic command must be specified for an address family or the system defaults for the timers basic command are used regardless of what is configured for RIP routing. The VRF does not inherit the timer values from the base RIP configuration. The VRF will always use the system default timers unless explicitly changed using the timers basic command.
See the "Address Family Timers: Example" section at the end of this chapter for examples of adjusting timers for an address family (VRF).
RIP Route Summarization
Summarizing routes in RIP Version 2 improves scalability and efficiency in large networks. Summarizing IP addresses means that there is no entry for child routes (routes that are created for any combination of the individual IP addresses contained within a summary address) in the RIP routing table, reducing the size of the table and allowing the router to handle more routes.
Summary IP address functions more efficiently than multiple individually advertised IP routes for the following reasons:
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When RIP determines that a summary address is required in the RIP database, a summary entry is created in the RIP routing database. As long as there are child routes for a summary address, the address remains in the routing database. When the last child route is removed, the summary entry also is removed from the database. This method of handling database entries reduces the number of entries in the database because each child route is not listed in an entry, and the aggregate entry itself is removed when there are no longer any valid child routes for it.
RIP Version 2 route summarization requires that the lowest metric of the "best route" of an aggregated entry, or the lowest metric of all current child routes, be advertised. The best metric for aggregated summarized routes is calculated at route initialization or when there are metric modifications of specific routes at advertisement time, and not at the time the aggregated routes are advertised.
The ip summary-address rip router configuration command causes the router to summarize a given set of routes learned via RIP Version 2 or redistributed into RIP Version 2. Host routes are especially applicable for summarization.
See the "Route Summarization: Example" section at the end of this chapter for examples of using split horizon.
You can verify which routes are summarized for an interface using the show ip protocols EXEC command. You can check summary address entries in the RIP database. These entries will appear in the database only if relevant child routes are being summarized. To display summary address entries in the RIP routing database entries if there are relevant routes being summarized based upon a summary address, use the show ip rip database command in EXEC mode. When the last child route for a summary address becomes invalid, the summary address is also removed from the routing table.
Split Horizon Mechanism
Normally, routers that are connected to broadcast-type IP networks and that use distance-vector routing protocols employ the split horizon mechanism to reduce the possibility of routing loops. Split horizon blocks information about routes from being advertised by a router out of any interface from which that information originated. This behavior usually optimizes communications among multiple routers, particularly when links are broken. However, with nonbroadcast networks (such as Frame Relay and Switched Multimegabit Digital System [SMDS]), situations can arise for which this behavior is less than ideal. For these situations, you may want to disable split horizon with RIP.
If an interface is configured with secondary IP addresses and split horizon is enabled, updates might not be sourced by the secondary address. One routing update is sourced per network number unless split horizon is disabled.
Interpacket Delay for RIP Updates
By default, the software adds no delay between packets in a multiple-packet RIP update being sent. If you have a high-end router sending to a low-speed router, you might want to add such interpacket delay to RIP updates, in the range of 8 to 50 milliseconds.
RIP Optimization over WAN Circuits
Routers are used on connection-oriented networks to allow potential connectivity to many remote destinations. Circuits on the WAN are established on demand and are relinquished when the traffic subsides. Depending on the application, the connection between any two sites for user data could be short and relatively infrequent.
Source IP Addresses
By default, the software validates the source IP address of incoming RIP routing updates. If that source address is not valid, the software discards the routing update. You might want to disable this feature if you have a router that is "off network" and you want to receive its updates. However, disabling this feature is not recommended under normal circumstances.
Neighbor Router Authentication
You can prevent your router from receiving fraudulent route updates by configuring neighbor router authentication. When configured, neighbor authentication occurs whenever routing updates are exchanged between neighbor routers. This authentication ensures that a router receives reliable routing information from a trusted source.
Without neighbor authentication, unauthorized or deliberately malicious routing updates could compromise the security of your network traffic. A security compromise could occur if an unfriendly party diverts or analyzes your network traffic. For example, an unauthorized router could send a fictitious routing update to convince your router to send traffic to an incorrect destination. This diverted traffic could be analyzed to learn confidential information about your organization or merely used to disrupt your organization's ability to effectively communicate using the network. Neighbor authentication prevents any such fraudulent route updates from being received by your router.
When neighbor authentication has been configured on a router, the router authenticates the source of each routing update packet that it receives. This is accomplished by the exchange of an authenticating key (sometimes referred to as a password) that is known to both the sending and the receiving router.
There are two types of neighbor authentication used: plain text authentication and Message Digest Algorithm Version 5 (MD5) authentication. Both forms work in the same way, with the exception that MD5 sends a "message digest" instead of the authenticating key itself. The message digest is created using the key and a message, but the key itself is not sent, preventing it from being read while it is being transmitted. Plain text authentication sends the authenticating key itself over the wire.
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In plain text authentication, each participating neighbor router must share an authenticating key. This key is specified at each router during configuration. Multiple keys can be specified with some protocols; each key must then be identified by a key number.
In general, when a routing update is sent, the following authentication sequence occurs:
Step 1
The receiving (neighbor) router checks the received key against the same key stored in its own memory.
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MD5 authentication works similarly to plain text authentication, except that the key is never sent over the wire. Instead, the router uses the MD5 algorithm to produce a "message digest" of the key (also called a "hash"). The message digest is then sent instead of the key itself. This ensures that nobody can eavesdrop on the line and learn keys during transmission.
Another form of neighbor router authentication is to configure key management using key chains. When you configure a key chain, you specify a series of keys with lifetimes, and the Cisco IOS software rotates through each of these keys. This decreases the likelihood that keys will be compromised. To find complete configuration information for key chains, refer to the "Managing Authentication Keys" section in the "Configuring IP Routing Protocol-Independent Features" module of the Cisco IOS IP
Routing: Protocol-Independent Configuration Guide.IP-RIP Delay Start
The IP-RIP Delay Start feature is used on Cisco routers to delay the initiation of RIPv2 neighbor sessions until the network connectivity between the neighbor routers is fully operational, thereby ensuring that the sequence number of the first MD5 packet that the router sends to the non-Cisco neighbor router is 0. The default behavior for a router configured to establish RIPv2 neighbor sessions with a neighbor router using MD5 authentication is to start sending MD5 packets when the physical interface is up.
The IP-RIP Delay Start feature is often used when a Cisco router is configured to establish a RIPv2 neighbor relationship using MD5 authentication with a non-Cisco device over a Frame Relay network. When RIPv2 neighbors are connected over Frame Relay, it is possible for the serial interface connected to the Frame Relay network to be up while the underlying Frame Relay circuits are not yet ready to transmit and receive data. When a serial interface is up and the Frame Relay circuits are not yet operational, any MD5 packets that the router attempts to transmit over the serial interface are dropped. When MD5 packets are dropped because the Frame Relay circuits over which the packets need to be transmitted are not yet operational, the sequence number of the first MD5 packet received by the neighbor router after the Frame Relay circuits become active will be greater than 0. Some non-Cisco routers will not allow an MD5-authenticated RIPv2 neighbor session to start when the sequence number of the first MD5 packet received from the other router is greater than 0.
The differences in vendor implementations of MD5 authentication for RIPv2 are probably a result of the ambiguity of the relevant RFC (RFC 2082) with regards to packet loss. RFC 2082 suggests that routers should be ready to accept either a sequence number of 0 or a sequence number higher than the last sequence number received. For more information about MD5 message reception for RIPv2, see section 3.2.2 of RFC 2082 at the following url: http://www.ietf.org/rfc/rfc2082.txt.
Offset-list
An offset list is the mechanism for increasing incoming and outgoing metrics to routes learned via RIP. This is done to provide a local mechanism for increasing the value of routing metrics. Optionally, you can limit the offset list with either an access list or an interface.
Timers
Routing protocols use several timers that determine such variables as the frequency of routing updates, the length of time before a route becomes invalid, and other parameters. You can adjust these timers to tune routing protocol performance to better suit your internetwork needs. You can make the following timer adjustments:
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It also is possible to tune the IP routing support in the software to enable faster convergence of the various IP routing algorithms, and, hence, quicker fallback to redundant routers. The total effect is to minimize disruptions to end users of the network in situations where quick recovery is essential.
How to Configure RIP
This section contains the following tasks:
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Enabling RIP and Configuring RIP Parameters
Perform the steps in this section to enable RIP and to configure RIP parameters.
SUMMARY STEPS
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Specifying a RIP Version and Enabling Authentication
Perform this task to specify a RIP version and enable authentication.
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Summarizing RIP Routes
RIP Version 2 supports automatic route summarization by default. The software summarizes subprefixes to the classful network boundary when classful network boundaries are crossed. If you have disconnected subnets, disable automatic route summarization to advertise the subnets. When route summarization is disabled, the software sends subnet and host routing information across classful network boundaries. To disable automatic summarization, use the no auto-summary command in router configuration mode.
Restrictions
Supernet advertisement (advertising any network prefix less than its classful major network) is not allowed in RIP route summarization, other than advertising a supernet learned in the routing tables. Supernets learned on any interface that is subject to configuration are still learned. For example, the following summarization is invalid: (invalid supernet summarization)
Router(config)# interface Ethernet 1Router(config-if)# ip summary-address rip 10.0.0.0 252.0.0.0..SUMMARY STEPS
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DETAILED STEPSEnabling or Disabling Split Horizon
To enable or disable split horizon, use the following commands in interface configuration mode, as needed.
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DETAILED STEPSDisabling the Validation of Source IP Addresses
Perform this task to disable the default function that validates the source IP addresses of incoming routing updates.
Restrictions
Split horizon for Frame Relay and SMDS encapsulation is disabled by default. Split horizon is not disabled by default for interfaces using any of the X.25 encapsulations. For all other encapsulations, split horizon is enabled by default.
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Configuring Interpacket Delay
Perform this to configure interpacket delay.
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Optimizing RIP over WAN
There are two problems when RIP is not optimized:
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To overcome these limitations, triggered extensions to RIP cause RIP to send information on the WAN only when there has been an update to the routing database. Periodic update packets are suppressed over the interface on which this feature is enabled. RIP routing traffic is reduced on point-to-point, serial interfaces. Therefore, you can save money on an on-demand circuit for which you are charged for usage. Triggered extensions to RIP partially support RFC 2091, Triggered Extensions to RIP to Support Demand Circuits.
Perform the following task to enable triggered extensions to RIP and to display the contents of the RIP private database.
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Configuring IP-RIP Delay Start for Routers Connected by a Frame Relay Network
The tasks in this section explain how to configure a router to use the IP-RIP Delay Start feature on a Frame Relay interface.
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Timesaver
Prerequisites
Your router must be running Cisco IOS Release 12.4(12) or a later release.
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Restrictions
The IP-RIP Delay Start feature is required only when your Cisco router is configured to establish a RIPv2 neighbor relationship with a non-Cisco device and you want to use MD5 neighbor authentication.
Configuring RIPv2
This required task configures RIPv2 on the router.
This task provides instructions for only one of the many possible permutations for configuring RIPv2 on your router.
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DETAILED STEPSConfiguring Frame Relay on a Serial Subinterface
This required task configures a serial subinterface for Frame Relay.
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Configuring IP, MD5 Authentication for RIPv2 and the IP-RIP Delay Start Feature on a Frame Relay Subinterface
This required task configures IP, MD5 authentication for RIPv2 and the IP-RIP Delay Start feature on a Frame Relay subinterface.
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Configuration Examples for RIP
This section provides the following RIP configuration examples:
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Route Summarization: Example
The following example shows how the ip summary-address rip router configuration command can be used to configure summarization on an interface. In this example, the subnets 10.1.3.0/25, 10.1.3.128/25, 10.2.1.0/24, 10.2.2.0/24, 10.1.2.0/24 and 10.1.1.0/24 can be summarized as shown below while sending the updates over an interface.
Router(config)#interface GigabitEthernet 0/2Router(config-if)#ip summary-address rip 10.1.0.0 255.255.0.0Router(config-if)#ip summary-address rip 10.2.0.0 255.255.0.0Router(config-if)#ip summary-address rip 10.3.0.0 255.255.0.0Split Horizon: Examples
Two examples of configuring split horizon are provided.
Example 1
The following configuration shows a simple example of disabling split horizon on a serial link. In this example, the serial link is connected to an X.25 network.
Router(config)# interface Serial 0Router(config-if)# encapsulation x25Router(config-if)# no ip split-horizonExample 2
In the next example, Figure 1 illustrates a typical situation in which the no ip split-horizon interface configuration command would be useful. This figure depicts two IP subnets that are both accessible via a serial interface on Router C (connected to a Frame Relay network). In this example, the serial interface on Router C accommodates one of the subnets via the assignment of a secondary IP address.
The Ethernet interfaces for Router A, Router B, and Router C (connected to IP networks 10.13.50.0, 10.155.120.0, and 10.20.40.0, respectively all have split horizon enabled by default, while the serial interfaces connected to networks 172.16.1.0 and 192.168.1.0 all have split horizon disabled with the no ip split-horizon command. Figure 1 shows the topology and interfaces.
Figure 1 Disabled Split Horizon Example for Frame Relay Network
In this example, split horizon is disabled on all serial interfaces. Split horizon must be disabled on Router C in order for network 172.16.0.0 to be advertised into network 192.168.0.0 and vice versa. These subnets overlap at Router C, interface S0. If split horizon were enabled on serial interface S0, it would not advertise a route back into the Frame Relay network for either of these networks.
Configuration for Router A
interface ethernet 1ip address 10.13.50.1!interface serial 1ip address 172.16.2.2encapsulation frame-relayno ip split-horizonConfiguration for Router B
interface ethernet 2ip address 10.155.120.1!interface serial 2ip address 192.168.1.2encapsulation frame-relayno ip split-horizonConfiguration for Router C
interface ethernet 0ip address 10.20.40.1!interface serial 0ip address 172.16.1.1ip address 192.168.1.1 secondaryencapsulation frame-relayno ip split-horizonAddress Family Timers: Example
The following example shows how to adjust individual address family timers. Note that the address family "notusingtimers" will use the system defaults of 30, 180, 180, and 240 even though timer values of 5, 10, 15, and 20 are used under the general RIP configuration. Address family timers are not inherited from the general RIP configuration.
Router(config)# router ripRouter(config-router)# version 2Router(config-router)# timers basic 5 10 15 20Router(config-router)# redistribute connectedRouter(config-router)# network 5.0.0.0Router(config-router)# default-metric 10Router(config-router)# no auto-summaryRouter(config-router)#Router(config-router)# address-family ipv4 vrf abcRouter(config-router-af)# timers basic 10 20 20 20Router(config-router-af)# redistribute connectedRouter(config-router-af)# network 10.0.0.0Router(config-router-af)# default-metric 5Router(config-router-af)# no auto-summaryRouter(config-router-af)# version 2Router(config-router-af)# exit-address-familyRouter(config-router)#Router(config-router)# address-family ipv4 vrf xyzRouter(config-router-af)# timers basic 20 40 60 80Router(config-router-af)# redistribute connectedRouter(config-router-af)# network 20.0.0.0Router(config-router-af)# default-metric 2Router(config-router-af)# no auto-summaryRouter(config-router-af)# version 2Router(config-router-af)# exit-address-familyRouter(config-router)#Router(config-router)# address-family ipv4 vrf notusingtimersRouter(config-router-af)# redistribute connectedRouter(config-router-af)# network 20.0.0.0Router(config-router-af)# default-metric 2Router(config-router-af)# no auto-summaryRouter(config-router-af)# version 2Router(config-router-af)# exit-address-familyRouter(config-router)#IP-RIP Delay Start on a Frame Relay Interface: Examples
This excerpt from a router configuration file contains the minimum commands required to configure the IP-RIP Delay Start feature on your router.
!key chain rip-md5key 123456key-string abcde!router ripversion 2network 172.16.0.0no auto-summary!interface Serial3/0no ip addressencapsulation frame-relay ietfframe-relay lmi-type ansi!interface Serial3/0.1 point-to-pointip address 172.16.10.1 255.255.255.0ip rip initial-delay 45ip rip authentication mode md5ip rip authentication key-chain rip-md5frame-relay interface-dlci 100!
Additional References
The following sections provide references related to configuring Routing Information Protocol.
Related Documents
Standards
MIBs
RFCs
RFC 1058
Routing Information Protocol
RFC 2082
RIP-2 MD5 Authentication
RFC 2091
Triggered Extensions to RIP to Support Demand Circuits
RFC 2453
RIP version 2
Technical Assistance
Feature Information for Configuring RIP
Table 1 lists the features in this module and provides links to specific configuration information.
Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Note
Table 1 Feature Information for Configuring Routing Information Protocol
IP-RIP Delay Start
12.4(12)
15.0(1)M
12.2(33)SREThe IP-RIP Delay Start feature is used on Cisco routers to delay the initiation of RIPv2 neighbor sessions until the network connectivity between the neighbor routers is fully operational, thereby ensuring that the sequence number of the first MD5 packet that the router sends to the non-Cisco neighbor router is 0. The default behavior for a router configured to establish RIPv2 neighbor sessions with a neighbor router using MD5 authentication is to start sending MD5 packets when the physical interface is up.
The following sections provide information about this feature:
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The following commands were introduced or modified: ip rip initial-delay delay.
IP Summary Address for RIPv2
12.0(7)T
12.1(3)T
12.1(14)
12.2(2)T
12.2(27)SBB
15.0(1)M
12.2(33)SRE
15.0SThe IP Summary Adddress for RIPv2 feature introduced the ability to summarize routes. Summarizing routes in RIP Version 2 improves scalability and efficiency in large networks. Summarizing IP addresses means that there is no entry for child routes (routes that are created for any combination of the individual IP addresses contained within a summary address) in the RIP routing table, reducing the size of the table and allowing the router to handle more routes.
The following sections provide information about this feature:
The following commands were introduced or modified by this feature: ip summary-address rip.
Routing Information Protocol
12.2(27)SBB
15.0(1)M
12.2(33)SRE
15.0SRouting Information Protocol (RIP) is a commonly used routing protocol in small to medium TCP/IP networks. It is a stable protocol that uses a distance-vector algorithm to calculate routes.
Triggered RIP
12.0(1)T
15.0(1)M
12.2(33)SRE
15.0STriggered RIP was introduced to overcome constant RIP updates over expensive circuit-based WAN links. Triggered extensions to RIP cause RIP to send information on the WAN only when there has been an update to the routing database. Periodic update packets are suppressed over the interface on which this feature is enabled. RIP routing traffic is reduced on point-to-point, serial interfaces.
The following sections provide information about this feature:
The following commands were introduced or modified: ip rip triggered, show ip rip database.
Glossary
address family—A group of network protocols that share a common format of network address. Address families are defined by RFC 1700.
IS-IS—Intermediate System-to-Intermediate System. OSI link-state hierarchical routing protocol based on DECnet Phase V routing, where routers exchange routing information based on a single metric, to determine network topology.
RIP—Routing Information Protocol.RIP is a dynamic routing protocol used in local and wide area networks.
VRF—VPN routing and forwarding instance. A VRF consists of an IP routing table, a derived forwarding table, a set of interfaces that use the forwarding table, and a set of rules and routing protocols that determine what goes into the forwarding table. In general, a VRF includes the routing information that defines a customer VPN site that is attached to a PE router.
Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1005R)
Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.
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