Routing Question - Duplicate Route???

Unanswered Question
Apr 2nd, 2007

Would this routing table cause any issues? Mainly concerned with the and

show ip route

Routing entry for, 5 known subnets

Variably subnetted with 3 masks

Redistributing via eigrp 1

D [90/63232] via, 07:07:16, Vlan100

D EX [170/63232] via, 07:07:16, Vlan100

D [90/63232] via, 07:07:17, Vlan100

D EX [170/63232] via, 07:07:17, Vlan100

D [90/65792] via, 00:37:19, Vlan100

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (1 ratings)
Danilo Dy Mon, 04/02/2007 - 07:31

The more specific route (longer prefix /30) will take priority over less specific route (shorter prefix /24). Therefore, will be routed to All other host under (except and will be routed to

Richard Burts Mon, 04/02/2007 - 07:32


I do not see anything here that would cause issues. I see that EIGRP has learned 5 entries about the addres space: it has learned a /24 from one neighbor (, it has learned a more specific /30 and /32 from another neighbor (, and it has learned another more specific /30 and /32 from a third neighbor (

I am not sure what it means but I note that the /32 address is included within the /30 subnet and is advertised as EIGRP external so the /32 came via redistribution of something whle the /30 came via a network statement.

It is not a problem to have multiple entries which in a sense overlap each other or are contained within each other. The /32 is within the /30 which is within the /24. The way that IOS does route lookup is on the basis of longest match. So even though different neighbors are advertising different parts of the address space we should route to the correct neighbor.



Jon Marshall Mon, 04/02/2007 - 10:29


Rick has covered this in great detail. The only thing i would like to add is that if your link to goes down then the next best route will be chosen, in this case via This may or may not be what you want depending on the topology of your network, speed of links etc.




This Discussion