Rip V2 problem with subnet masks

[agentflicker]

Hello all,

I hope someone can tell me what I'm doing wrong here. I think this should be fairly basic to someone who knows what they are doing, but unfortunatly I don't.

I have a network I'm attempting to setup like this:

|
Firewall
|
|
|
CoreRouter
|.1
|
172.20.2.0/26
|
---------Hub----------
| |
| |
|.6 |.7
Router1a Router2a
| |
Serial Serial
| |
Router1b Router2b
| |
172.16.4.0/22 172.16.8.0/22

The routers are all running IOS ver 12.0 and
What I am trying to do is setup RIPv2 to advertise from router1b and router2b that they have the 172.16.4.0/22 and 172.16.8.0/22 networks connected to them so if the Corerouter needs to route a packet back to say "172.16.4.3" the Corerouter will know to send it via Router1a.

The RIP is working and sending routing updates to the CoreRouter but on router1b when I type in:
#router rip
#version 2
#network 172.16.4.0
and then go show running-config
it shows:
>router rip
> version 2
> network 172.16.0.0

and then on the CoreRouter I go
#show ip route
I get:
R 172.16.0.0/16 [120/1] via 172.20.2.6, 00:00:27, Ethernet1
[120/1] via 172.20.2.8, 00:00:09,

So basically it doesn't seem to care about the subnet mask only the major network portion, ie 172.16.0.0.

Whats going wrong or is what I'm trying to do just not possible?

Cheers Simon.

 

[wybnormal]

You did not say if ALL the routers are talking RIP2. All least routers 1b,2b and the core need to have RIP2 for all them to understand the subnet mask. RIP1 is classful and break things down on the standard /24 mask.

What does the command "show ip route" give you? you should see the subnet and then a notice that it has been subnetted along with the subnets.

Here is a very good tutorial on RIP from Cisco's Packet Magazine.

http://www.cisco.com/warp/public/784/packet/jul01/p27-enterprise.html#title

MikeS Find me at

http://www.packetattack.com

"The trouble with giving up civil rights is that you never get them back"

 

[mesagreg]

Instead of entering:

network 172.16.4.0

in your CoreRouter, try this;

network 172.16.0.0

put this in all routers running RIP. It appears that Routers 2a & 2b may not be running RIP. Make sure that they are, and that their network statements are the same as above.

Hope this helps,

Greg

 

[agentflicker]

Thanks guys,

All the routers are running RIPv2. What I also tried was to configure the serial interfaces on Routers 1a and 2a as 172.16.4.1/22 and 172.16.8.1/22 and disconnected routers 1b and 2b.

here is the full print out from:
#sh ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default
U - per-user static route, o - ODR

Gateway of last resort is 172.20.1.9 to network 0.0.0.0

R 172.16.0.0/16 [120/1] via 172.20.2.6, 00:00:27, Ethernet1
[120/1] via 172.20.2.8, 00:00:09, Ethernet1
172.20.0.0/26 is subnetted, 1 subnets
C 172.20.2.0 is directly connected, Ethernet1
S* 0.0.0.0/0 [1/0] via 172.20.1.9


So you can see the local "C" route has the subnettted info but the RIP routes so not, and this is what is causing my problem.

Cheers Simon.

 

[svermill]

Simon,

Is 'ip classless' enabled by default with RIP v2?

Scott

 

[agentflicker]

To all who replied,

Thanks I think I have sorted it out now. On all the routers involved I added:
#router rip
#no auto-summary

now my routing table looks like this:

Gateway of last resort is 172.20.1.9 to network 0.0.0.0

172.16.0.0/22 is subnetted, 2 subnets
R 172.16.8.0 [120/1] via 172.20.2.8, 00:00:16, Ethernet1
R 172.16.4.0 [120/1] via 172.20.2.6, 00:00:14, Ethernet1
172.20.0.0/16 is variably subnetted, 2 subnets, 2 masks
C 172.20.1.8/29 is directly connected, Ethernet0
C 172.20.2.0/26 is directly connected, Ethernet1
S* 0.0.0.0/0 [1/0] via 172.20.1.9

Which is showing all the subnet info that I need, so I guess the auto-summary was dropping the subnet info.

Simon.

 

[svermill]

Simon,

Good work. And thanks for the update. Just FYI: EIGRP has the same classful default behavior. It too requires 'no auto-summary' in the config.

Scott