Routes not exchanged via EIGRP

[dev35]

Please refer to the attached diagram.
R1,7K-A ,7K-B are EIGRP neighbors with each other, There are no issues with the neighborship and no filter's applied.
7K-A & 7K-B can learn route 172.16.0.0/16 from R1 but the same route is not exchanged between 7K-A & 7K-B via EIGRP.
No issue between the 7K-A & 7K-B EIGRP neighborship and I see other routes are getting exchanged.
I have considered split horizon rule, but that should not apply here as the routes need to be exchanged via different interfaces.
Any ideas on what might be causing this issue?

[David Ruess · Accepted solution]

Hello,

Your'e not running into the Split Horizon Rule but you're likely running into the DUAL Algorithm.

If you check the topology table using the all-links keyword you should see that each router is learning that network from each other but not installed into the routing table because of Feasible Distance. I wont use the route through my neighbor (A or B because I have my best path through R1 as both routers see.

Can you show the output of the topology table on both routers using the all-links keyword?

Another test you can do is shut down the interface going to R1 on one of the routers and if as you say neighborships are up and exchanging routes then the router will learn the 172.16.0.0/16 network through its other neighbor when the DUAL loop free algorithm runs.

-David

[paul driver]

Hello
I agree with @David Ruess  dual is what you are seeing, another test is to add some delay to one of the links between either 7K1-A/B and rtr1

[dev35]

Sorry, I forgot to mention that I do not see the route in the eigrp topology table.
As per my understanding even if the route do not pass the feasibility condition, The route should be in the topology table of the eigrp.

[paul driver]

Hello

Do you see it when you run this command? - sh ip eigrp topology all-links
if not check the eigrp router-ids of both NK7 rtrs they should not be the same for if they are then they can potentially filter each others routes.
sh ip protocols | in Router-ID

[David Ruess]

As @paul driver stated and I mention above use the all-links keyword (show ip eigrp topology all-links) as that shows routes that didn't pass the feasibility condition. Without that keyword it may not show all learned routes.

Can you also provide the output of the commands you use to help us troubleshoot further?

-David

[MHM Cisco World]

I dont think it split horizon 
can I know how you interconnect both router ? 
are it router or L3 SW becuase I see you use VLAN 187?
if it L3SW how you make VLAN187 have two different subnet ?

MHM

[dev35]

Sorry, False positive, When I was checking I did not include all-links in the sh ip eigrp topology command.