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Eirgrp Routing

Dynamic routing EIGRP running on all router and L3 switches on both sites.

Two ISP circuits between sites. 10MB lease line and 2MB Serial circuit.

Problem:

On switch (Sw-SideA), when I run 'shop ip eigrp topology I only see one route to 10.60.0.0/24 network, I was expecting to see two routes over both routers (R1-SideA & R1-SideB)

Please advise

R1-SideA

router eigrp 1

network 10.0.0.0

no auto-summary

R2-SideA

router eigrp 1

network 10.0.0.0

no auto-summary

Sw-SideA

router eigrp 1

network 10.0.0.0

no auto-summary

R1-SideB

router eigrp 1

network 10.0.0.0

no auto-summary

R2-SideB

router eigrp 1

network 10.0.0.0

no auto-summary

Sw-SideB

router eigrp 1

network 10.0.0.0

no auto-summary

3 REPLIES

Re: Eirgrp Routing

Hi Colm,

Is Sw-SideA to R2-SideA and Sw-SideB to R2-SideB a routed port or a switchport?

Lejoe

Hall of Fame Super Silver

Re: Eirgrp Routing

Hello Colm,

first of all I would verify that EIGRP neighborship is built on vlan 61 between SW-sideA and R2-SideB.

The second note is that it is possible that in normal conditions R2-SideB uses vlan61 to reach the route and so it is seen as a downstream router:

to be listed in the eigrp topology table as a feasible successor the route advertised by R2-SideB must pass the feasibility test:

metric or R2-SideB < best metric to the route

if R2 uses the path via SW-SideA it is seen as more far from the destination route and so it is not installed in the EIGRP table.

Actually R2-Side B itself once decides that the path via vlan 61 is better applies split horizon and removes its advertisement of the route out vlan 61

(doesn't advertise out an inteface what it learns on the same link)

So what yo see is correct behaviour because the EIGRP metric is proportional to sums of delay and to the inverse of lowest bandwidth in path.

To check just do

sh ip route network

on R2-Sideb and see if the outgoing inteface is vlan61 to SW-SideA

Hope to help

Giuseppe

New Member

Re: Eirgrp Routing

You only see that route because it is the better route and the route via the 10.254.0.0 network does not pass the feasible successor test; if the Reported Distance (RD) for 10.254.0.0 is larger than the Feasible Distance (FD) via 10.255.0.0 then this route is NOT entered into the Topology Table as a Feasible Successor. You could tweak this by manipulating the bandwidth and delay values along the path to insure the route was installed.

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