Router RIP Configuration

[nelson.garcia]

Hey guys, I'm using GNS3 to try out some labtas I've been thinking of. I've got this one where I'm setting up RIP and I'm stuck. I've attached a picture of the topology so you can see for yourself.

Here's my problem.

When I enable RIP on all the routers and then do a debug, they are sending out advertisements on their Fast Ethernet interfaces and not on the Serial links.

I want to point out that all routers on the left hand side are on the same network and can ping each other. Same for the right side.

I would like the routers connecting on Serial links to exchange routing updates to each other advertising the networks they are connected to, but they don't.

When I add a static route to, let's say, R3, like this ip route 10.1.0.0 255.255.0.0 serial1/0, I can ping only the Fast Ethernet interface on R5 and not any of the other routers that are also on the 10.1.0.0 network.

Please note: SW1 and SW2 are routers with a 16-port Fast Ethernet module. This is the way to do switching in GNS3.

[Giuseppe Larosa]

Hello Nelson,

routers need a network command that match serial interface IP subnet in order to send out advertisements and you have used IP subnets that are part of other major networks on the serial interfaces

so R3

router rip

network 10.0.0.0

network 1.0.0.0

!

R5

network 10.0.0.0

network 1.0.0.0

!

Hope to help

Giuseppe

[nelson.garcia]

I understand that I've used IP blocks assigned to other entities, but for simplicity sake, I used them anyway.

One thing I don't understand is why you used networks 10.0.0.0 and 1.0.0.0 in the network statement for R3 and R5.

I thought with RIP you had to enter the networks that the router directly connects to. So for routers R3 and R4, since they are both on subnets

10.8.0.0/16, the network statement would be, 'network 10.8.0.0'.

Also, would you happen to know why the edge routers advertise RIP updates on their Fast Ethernet interfaces and not on their Serial interfaces?

[nelson.garcia]

Hey, I tried out your config on both R3 and R5 and they still aren't sending routing updates to each other. They are still trying to send updates out of their Fast Ethernet interfaces.

After applying your configuration, here are the outputs of 'show ip route'

R3:

2.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C        2.2.2.0/24 is directly connected, Serial1/0

L        2.2.2.1/32 is directly connected, Serial1/0

      10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C        10.8.0.0/16 is directly connected, FastEthernet0/0

L        10.8.1.1/32 is directly connected, FastEthernet0/0

R5:

2.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C        2.2.2.0/24 is directly connected, Serial1/0

L        2.2.2.2/32 is directly connected, Serial1/0

      10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C        10.1.0.0/16 is directly connected, FastEthernet0/0

L        10.1.1.9/32 is directly connected, FastEthernet0/0

As you can see, neither router has any routing information for the other's connected networks.

[Giuseppe Larosa · Accepted solution]

Hello Nelson

I apologize I made a little mistake before

please use the following

R3

router rip

network 10.0.0.0

network 2.0.0.0

!

R5

router rip

network 10.0.0.0

network 2.0.0.0

the basic idea is that the network command in IGP dynamic routing protocols provide different tasks:

- advertise the IP subnets that match the network command

- allow to send advertisements out interfaces with an IP address that match the network command

- allow to receive advertisements on  interfaces with an IP address that match the network command

so for having R3 and R5 to speak RIP on the serial link, the IP subnet of the serial link must match a

network command

>> C        2.2.2.0/24 is directly connected, Serial1/0

of course you can use more specific network commands as you like

Hope to help

Giuseppe

[nelson.garcia]

Giuseppe, thanks for the reply, man, it worked like a charm. And thanks for the explanation on the network statement, I'll be sure to add it to my notes.

Take care,

Nelson