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Routers A, B & C live at 10.1.1.1, 10.1.1.2 and 10.1.1.3 on a /24 metro Ethernet subnet. Each router also has its own private subnet on another interface. Router B's private subnet links thru a firewall to a 10.20.20.0 network at another organization.

Router B redistributes to A and C several static routes for hosts on 10.20.20.0. However, a new host 10.20.20.5/32 must be reached via a different path that goes through router C. I know that C can advertise this host-based route with no problem, but I'd like to keep all my 10.20.20.x static routes in one place.

So, how can B tell A via RIPv2 to send packets for 10.20.20.5/32 to C?

So far it looks like I need no ip split-horizon on router B's 10.1.1.2 interface, perhaps because B has already learned from C other routes with a next hop of 10.1.1.3. But how does RIPv2 split horizon with no auto-summary and network 10.0.0.0 really work? If B learns a route to ANY 10.x.x.x network or host from A or C, is that enough for split horizon to keep it from redistributing ip route 10.20.20.5 255.255.255.255 10.1.1.3?

And if I want to suspend split horizon only for this one new host, how do I filter out the mess of regurgitated routes that B advertises when I try no ip split-horizon?

Thanks much.

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  • Why does B have to tell A to route via C, why don't you originate the route from C? Are you originate a /24 from B for 10.20.20.0/24? Even if that is the case, the more specific route form C should "win" and be put forward to the RIB on A and B for that single host.
    – Baldrick
    Nov 2, 2012 at 17:59
  • @javano Why? "I know that C can advertise this host-based route with no problem, but I'd like to keep all my 10.20.20.x static routes in one place."
    – Paul
    Nov 11, 2012 at 0:27
  • "I know that C can advertise this host-based route with no problem, but I'd like to keep all my 10.20.20.x static routes in one place." - That says to me you want to keep all these routes on B, but whats the point? With only three routers it almost a negligible amount of complexity for seemingly no measureable gain. As others have said you could just use "redistribute static" from C as you are going to need a static route there.
    – Baldrick
    Nov 11, 2012 at 11:48

2 Answers 2

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Maybe post the relevant parts of your config? I believe redistribute static on router should distribute the static routes that are on the router with that config. Do you not see the route on the routers when you run show ip route?

Also, I am a bit confused by what you mean with 'the routers share the same subnet'.... Wouldn't the hosts all then be on the same subnet, so the traffic will just go through the switches? I think you need to de-abstract your question a little, for example, paste IP address and subnets.

Keep in mind that redistribute static will redistribute all the static routes, use a route map to limit which static routes get redistributed. This cisco page says how.

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  • Thanks for the helpful link! Sorry for confusion...each router also has its own subnet on another interface for hosts. I updated question w/answer.
    – Paul
    Jan 7, 2010 at 3:00
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You are going to need a static route on router 'C' for the /32 host. You can also have a static on router 'B' for the same host pointing to router 'C' as the next hop, which you can then redistributed through RIP.

router B>
ip route 10.20.20.5 255.255.255.255 10.1.1.3

router rip
 version 2
 redistribute static

router C>
ip route 10.20.20.5 255.255.255.255 10.30.30.1

Are the networks behind the 'B' and 'C' router the same network? If yes, then you will probably have some asymmetric routing unless they also do some work on their routers.

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