RIP problem

balajee · ‎11-08-2007

Hi,

I have the following topology in my lab setup. I am using xxxx routers, not cisco devices.

30.30.30.0/24-|R1| - 10.10.10.0/24 - |R2|

- configured RIP between R1 and R2.

- Added few static routes in R1 like

"20.20.20.0/24 via 10.10.10.10" where 10.10.10.10 is not existing.

- Redistributed above said static routes into RIP on R1.

- These routes are not visible in R2.

- If I add a route like "40.40.40.0/24 via 30.30.30.100" and redistributed, then these routes are coming into R2.

Is there any specific reasong for this?

Thanks,

Balajee

bvsnarayana03 · ‎11-08-2007

What I understand is, you are not using 10.10.10.10 in your topology but route is pointed towards it. Now, routing tables contains entries for Prefix, Next-hop, interface & metric. When next-hop is not available, the route will not make entry in to the routing table & thus there is no chance for this route to be visible in the routing table of R2.

For 40.40.40.0, may be the next-hop is available thats why route appears on other router.

Richard Burts · ‎11-08-2007

Balajee

I believe that there is a somewhat different explanation for this behavior. It is a reflection of the fact that RIP uses classful routing and uses split horizon to prevent loops. If the static route specifies a next hop of 10.10.10.10 and if the 10.10.10.0 subnet is shared with R2 then RIP on R1 will not advertise the redistributed routes out that interface because that would be advertising toward the source of the route and RIP does not do that. When the static route has a next hop of 30.30.30.100 and the 30.30.30.0 network is not shared with R2 then R1 will advertise the route.

B V S is correct that if the next hop is not reachable then the static route will be withdrawn from the routing table and will not redistribute. But if the next hop address is within the subnet of a connected interface then IOS assumes that the next hop is reachable.

HTH

Rick

HTH

Rick