Tuning, Redistribution, and Controlling IGRP Updates

Configuring RIP-1 and RIP-2

The configuration of RIP-1 and RIP-2 is a straightforward task:

Step 1. Enable RIP and the version of RIP on the router. To enable RIP, use the router rip global command. At this time, also configure the version of RIP. If you want RIP-1, no additional configuration is necessary. For RIP-2, use the version 2 command from the config-router# prompt.

Step 2. Add the networks on which you want to want to run RIP. This is accomplished with the command network a.b.c.d from the config-router# prompt.

Configuring RIP-1

Example 9-3 illustrates the configuration of RIP-1 on the network previously illustrated in Figure 9-1.

Example 9-3 RIP-1 Configuration

  hostname wolverine   !   router rip   network 128.200.0.0   !  _______________________________________________________________________  hostname rogue   !   router rip   network 128.200.0.0   network 192.16.1.0   !  _______________________________________________________________________  hostname cyclops   !   router rip   network 192.16.1.0   !  

Configuring RIP-2

Let's update the network from Figure 9-1 to a RIP-2 network. You will configure the Token Ring network on wolverine to send and receive both RIP-1 and RIP-2 updates. The Ethernet segment off wolverine, however, will send and receive only Version 2 updates. The rogue and cyclops routers will be configured to send and receive only RIP-2 updates. Example 9-4 shows the necessary router configurations to match this criteria.

Example 9-4 RIP-2 Configuration

   hostname wolverine    !   interface Ethernet1   ip address 128.200.1.1 255.255.255.0    ip rip send version 2     ip rip receive version 2    media-type 10BaseT   !   interface TokenRing0   ip address 128.200.2.1 255.255.255.0    ip rip send version 1 2     ip rip receive version 1 2    ring-speed 16   !    router rip     version 2     network 128.200.0.0     no auto-summary    __________________________________________________________________________    hostname rogue    !   interface Ethernet0/0   ip address 128.200.1.2 255.255.255.0    ip rip send version 2     ip rip receive version 2    !   interface Ethernet0/1   ip address 192.16.1.5 255.255.255.252    ip rip send version 2     ip rip receive version 2    !    router rip     version 2     network 128.200.0.0     network 192.16.1.0     no auto-summary   ____________________________________________________________________   hostname cyclops    !   interface Ethernet0   ip address 192.16.1.6 255.255.255.252    ip rip send version 2     ip rip receive version 2    !    router rip     version 2     network 192.16.1.0     no auto-summary   

Figure 9-2 illustrates the changes in the routing tables after migrating the network to RIP-2. Notice how the individual subnets appear on wolverine and cyclops routers. Even though you are now sending RIP-2 updates, you must also use the no auto-summary command to prevent automatic summarization at the major class boundary.

Figure 9-2. Classless Routing Example

The "Big show" and "Big D" for RIP

Troubleshooting RIP can be an easy process. Most of the RIP configuration errors involve a bad network statement, discontinuous subnets, or split horizons. Because most of these errors are design- related , the debug and show commands for RIP are limited. Again, the list that follows is not a complete list; instead, it's a condensed list of what I find to the most useful show and debug commands. The "Big show " and the "Big D" commands for RIP are as follows:

• show ip protocols { summary }

• show ip route

• debug ip rip { events }

show ip protocols {summary} Command

This command displays all routing protocols, detailed timer and metric information, and routing update information. Example 9-5 lists the output of the show ip protocols command.

Example 9-5 show ip protocols Command Output

 rogue#  show ip protocols   Routing Protocol is "rip"  Routing Protocol Type  Sending updates every 30 seconds, next due in 29 seconds  Invalid after 180 seconds, hold down 180, flushed after 240  Timer information   Outgoing update filter list for all interfaces is  Distribut list (if any)  Incoming update filter list for all interfaces is  Default redistribution metric is 2  Default metric   Redistributing: rip, eigrp 2001  Redistrution is on  Default version control: send version 1, receive any version     Interface        Send  Recv   Key-chain  Ethernet0/0      1     1 2  RIP Versions running   Routing for Networks:  Networks participating in RIP  128.200.0.0   Passive Interface(s):  Ethernet0/1  Network listening to RIP  Routing Information Sources:     Gateway         Distance      Last Update  128.200.1.1          120      00:00:07  RIP Neighbors   Distance: (default is 120)  Administrative Distance  

show ip route Command

This command lists the router's current routing table and the one on which it makes forwarding decisions. It is possible for a route to exist or be known to the router but then have only the routes with the shortest administrative distances listed. The output from this command lists what routing protocol the route is from ”in the case of Example 9-6, R for RIP. The number behind the route is the administrative distance of the route followed by the hop count. The Via field explains who the route is from, how long ago an update was received, and by what interface. Example 9-6 lists the output of the show ip route command used on the rogue router.

Example 9-6 show ip route Command Output

 rogue#  show ip route  Gateway of last resort is not set      128.200.0.0/16 is variably subnetted, 4 subnets, 2 masks  R       128.200.10.0/24 [120/1] via 128.200.1.1, 00:00:17, Ethernet0/0  C       128.200.1.0/24 is directly connected, Ethernet0/0 R       128.200.2.0/24 [120/1] via 128.200.1.1, 00:00:17, Ethernet0/0 C       128.200.3.16/29 is directly connected, Ethernet0/1 rogue# 

In this example, the route 128.200.10.0/24 has a metric of 120 and is one hop away. The RIP neighbor informing about the route is 128.200.1.1, and it sent the last update 17 seconds ago; rogue received it through its Ethernet 0/0 port.

debug ip rip {events} Command

This command shows all the RIP activity occurring in the router and also displays exactly which interfaces are advertising and receiving routes. The RIP version of the update is also displayed, along with the metric of each route in the update. Example 9-7 lists the output of the debug ip rip command. Notice that RIP is sending and receiving routes.

Example 9-7 debug ip rip Command Output

 wolverine#  debug ip rip   1d02h: RIP: received v1 update from 128.200.10.2 on TokenRing1   1d02h:      128.200.10.0 in 1 hops  1d02h: RIP: sending v1 update to 255.255.255.255 via Ethernet1 (128.200.1.1) 1d02h:      subnet  128.200.10.0, metric 1 1d02h:      subnet  128.200.2.0, metric 1 1d02h: RIP: sending v1 update to 255.255.255.255 via TokenRing0 (128.200.2.1) 1d02h:      subnet  128.200.10.0, metric 1 1d02h:      subnet  128.200.1.0, metric 1  1d02h: RIP: sending v1 update to 128.200.10.2 via TokenRing1 (128.200.10.1)   1d02h:      subnet  128.200.10.0, metric 1   1d02h:      subnet  128.200.1.0, metric 1   1d02h:      subnet  128.200.2.0, metric 1