RIP Class C Routes

Brownie1985

Hi Guys, was hoping someone to help with a quick question

Would anyone be able to explain to myself why when using RIP with a no auto-summary a class c networks of say 192.168.0.0, 192.168.1.0, 192.168.2.0 are just listed as one route of

R 192.168.0.0/24 is up, routing via 10.10.10.1, FastEthernet0/0

Just to help explain, say you have three routers (2 interfaces each) plugged into a switch with each interface in the switch given an address of 10.10.0.0/24, then the other interfaces again plugged into its own switch with the interfaces having 192.168.0.0/24, 192.168.1.0/24, 192.168.2.0/24. With this setup the routes do no probigate to the other routes. But if I changes the 192.168.0.0 ranges to class B 172.16.0.0/24, 172.16.1.0/24, 172.16.2.0/24 the routes will propigate.

Is this due to the 192.168.0.0 address already being classed as a class C so the route that would be advertised when you enter command network 192.168.0.0 would be [192.168.0].0 with the last ].0 being the variable it would be looking to be different on the subnet?

Hope my ramble kinda makes sense for the question I am asking.

Thanks

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Comments

Eildor

Brownie1985 wrote: »

Hi Guys, was hoping someone to help with a quick question

Would anyone be able to explain to myself why when using RIP with a no auto-summary a class c networks of say 192.168.0.0, 192.168.1.0, 192.168.2.0 are just listed as one route of

R 192.168.0.0/24 is up, routing via 10.10.10.1, FastEthernet0/0

Just to help explain, say you have three routers (2 interfaces each) plugged into a switch with each interface in the switch given an address of 10.10.0.0/24, then the other interfaces again plugged into its own switch with the interfaces having 192.168.0.0/24, 192.168.1.0/24, 192.168.2.0/24. With this setup the routes do no probigate to the other routes. But if I changes the 192.168.0.0 ranges to class B 172.16.0.0/24, 172.16.1.0/24, 172.16.2.0/24 the routes will propigate.

Is this due to the 192.168.0.0 address already being classed as a class C so the route that would be advertised when you enter command network 192.168.0.0 would be [192.168.0].0 with the last ].0 being the variable it would be looking to be different on the subnet?

Hope my ramble kinda makes sense for the question I am asking.

Thanks

Are you running RIP version 2? What networks are listed when you do a "show ip protocols"?

Brownie1985

Version 2 is running on all routers with no auto-summary, just checked to make sure. Its odd as this all works fine when using a class b address subnetted to /24 - here is a quick output since changing back to 192.168.0.0 ranges

10.0.0.0/24 is subnetted, 2 subnets
C 10.10.10.0 is directly connected, FastEthernet0/0
R 10.10.20.0 [120/1] via 10.10.10.3, 00:00:20, FastEthernet0/0
172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
R 172.16.0.0/16 is possibly down, routing via 10.10.10.3, FastEthernet0/0
R 172.16.2.0/24 is possibly down, routing via 10.10.10.2, FastEthernet0/0
R 172.16.3.0/24 is possibly down, routing via 10.10.10.3, FastEthernet0/0
C 192.168.0.0/24 is directly connected, FastEthernet0/1

You can see it was picking up the router correctly when using 172.16.0.0 addresses and all the routers are using network 192.168.0.0. This is only something I have done in GNS, but cant get my head around why using class c address when work

Eildor

Brownie1985 wrote: »

Version 2 is running on all routers with no auto-summary, just checked to make sure. Its odd as this all works fine when using a class b address subnetted to /24 - here is a quick output since changing back to 192.168.0.0 ranges

10.0.0.0/24 is subnetted, 2 subnets
C 10.10.10.0 is directly connected, FastEthernet0/0
R 10.10.20.0 [120/1] via 10.10.10.3, 00:00:20, FastEthernet0/0
172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
R 172.16.0.0/16 is possibly down, routing via 10.10.10.3, FastEthernet0/0
R 172.16.2.0/24 is possibly down, routing via 10.10.10.2, FastEthernet0/0
R 172.16.3.0/24 is possibly down, routing via 10.10.10.3, FastEthernet0/0
C 192.168.0.0/24 is directly connected, FastEthernet0/1

You can see it was picking up the router correctly when using 172.16.0.0 addresses and all the routers are using network 192.168.0.0. This is only something I have done in GNS, but cant get my head around why using class c address when work

What happens if you were to disconnect the directly connected 192.168.0.0/24 network?

Is there a way for you to send me the GNS3 file?

Monkerz

What network commands are you using under each rip process?

"network 172.16.0.0" would advertise 172.16.0.0, 172.16.1.0 and 172.16.2.0, but "network 192.168.0.0" would only advertise 192.168.0.0.

I think this is what you were asking in your first post.

Eildor

Monkerz is right -- did you include network statements for each of the networks (192.168.x.0)?

Brownie1985

Monkerz wrote: »

What network commands are you using under each rip process?

"network 172.16.0.0" would advertise 172.16.0.0, 172.16.1.0 and 172.16.2.0, but "network 192.168.0.0" would only advertise 192.168.0.0.

I think this is what you were asking in your first post.

YESSS!!! Thats it, just quickly wizzed this up. I was looking at a completely different angle as how the classful network command works!

All makes sense now, as the 172.16.0.0 class B network has .16 as the last net mask, so other bits are expected to change, where as 192.168.0.0 class c expects that the .0 will stay the same as it's netmask goes to 192.168.0.

Thank you very much, can't believe I didn't see this. All the routes are as should be expected