Category Archives: Redistribution

Redistributing static routes on EIGRP stub routers

Ran into this little enigma while working with remote routers and distribution routers using EIGRP. At least, it’s always an enigma when you don’t know how it works, right?

The setup was fairly straightforward: two distribution routers talk to a remote router (configured as a stub in EIGRP), and the remote router has a static route to the subnet in question, 172.x.x.x/24 (see diagram below). How do you redistribute the 172 subnet back the core, through the distribution router?

Originally, I played with static routes. Static routes on Remote (to get a path through the firewall), and static routes on Dist 1 and a static route on the Core. Fine, it worked, but only provisionally. I could reach 172.x.x.x, but if Dist 1 failed, there was no automatic failover of the route. It had to be redistributed into EIGRP.

OK, that’s relatively simple – one one routing protocol, don’t have to work about weighting the metrics, no prob. Just to be sure I was only redistributing the route in question, and nothing else, I created a route map:

ip route 172.x.x.x 255.255.255.0 192.168.x.x (The original static route)

access-list 10 permit 172.x.x.x 0.0.0.255 (ACL identifying the 172.x.x.x subnet)

route-map 172.x.x.x_net permit 10 match ip address 10 (Route Map calling ACL 10)

So far so, good. Now, to redistribute the route into the EIRGP process:

router eigrp 1

redistribute static route-map 172.x.x.x_net

I looked at the eigrp topology table, and? Yes, 172.x.x.x does appear in the topology table:

P 172.19.39.0/25, 1 successors, FD is 28160 via Rstatic (28160/0)

All is well on the Remote router. Now, does the route appear in the Distribution Routers? I take a look at the EIGRP topology table there and? Nothing. Wait, what? Look again. Nothing.

Damn.

The route is making it into the EIGRP process on the remote, but isn’t being advertised to its peers. Why?

After some Googling, I run across this article:

http://www.cisco.com/en/US/docs/ios/12_0s/feature/guide/eigrpstb.html#wp1035883

It explains that in order to advertise redistributed static routes, you have to modify the stub configuration to allow the sending of redistributed static routes, thusly:

router eigrp 1

eigrp stub static

Now, when I check the Distribution Routers, there is the route, pretty as a sunrise on a morning in May.

Note to self: when redistributing static routes on EIGRP stub routers, redistribute first into EIGRP, and then be sure to modify the eigrp stub statement to allow advertisement of the route to EIGRP peers.


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