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New Member

injecting more specific routes into EIGRP

Hi,

I need the following:

I have Ethernet0/0 with 192.168.5.0/24 on the router that has two WAN circuits, MPLS and IPSEC'ed gre tunnel. both wan circuits go back to corporate. I have bgp running across MPLS and EIGRP across gre tunnels. GRE tunnels are backup for MPLS circuit. I advertise 192.168.5.0/24 through BGP and EIGRP. The BGP routes get redistributed back to EIGRP at the datacenter. with EIGRP @ remote site I advertise 192.168.5.0 as External route by:

redistribute connected route-map Redis-connected-rm

I also have /28 blocks within that 192.168.5.0 network that I want to be "pure" EIGRP all the way across, so the traffic to those IP's will go across GRE tunnel, not BGP.

here is the question:

how do I advertise /28 (more specific) networks at the remote site (as EIGRP internal) while I do not have them in the routing table? the routing table only has /24 network (which is being advertised as external).

I tried :

router eigrp 1

network 192.168.5.0 0.0.0.15

but it didn't work.

thanks.

  • WAN Routing and Switching
2 REPLIES
Hall of Fame Super Silver

Re: injecting more specific routes into EIGRP

John

Using a mask with the network statement in EIGRP does not change what EIGRP will advertise, it only changes the way that EIGRP checks interfaces to see which ones to include into the protocol processing.

EIGRP can not advertise a prefix to neighbors that is not in the routing table. If you have some /28 blocks of addresses that you want advertised you will need to get those blocks into the routing table. To do that I would suggest configuring static routes. The config might look something like:

I would change the network statement in EIGRP and remove the mask so it would be

network 192.168.5.0

ip route 192.168.5.64 255.255.255.240 FastEthernet0/0

ip route 192.168.5.128 255.255.255.240 FastEthernet0/0

In general I advise against using static routes pointing at LAN interfaces. But in this circumstance I think it would work well, and I believe that EIGRP would pick up these routes since they are covered by the network statement. If there is an issue with EIGRP picking up the address blocks you may need to redistribute static into EIGRP.

HTH

Rick

New Member

Re: injecting more specific routes into EIGRP

that idea worked, but I had to modify it slightly...

once you add "network 192.168.5.0" under "router eigrp" - it makes all traffic to this subnet go across gre tunnels.

instead, I added a route-map to filter those specific subnets from the bigger /24 network out, and then "redistribute static route-map blah" (of course I have 3 static routes as you suggested) ; everything works great. thanks for the hint!

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