EIGRP routes DO meet feasibility condition - yet not inserted as feasible successors...

[mmanthe]

Hello all!

I've got a home lab and have been doing some EIGRP 'noodling' and have run across something that currently has me stumped.

 For the purpose of this question, the topology is as follows:

The 'issue' seems to be with routes originally advertised FROM R3, TO R2 and then FROM R2, TO R1 on the serial links. Along with the physical interfaces, I've created several loopbacks on each router to 'pad' the routing tables and to have networks to experiment with (filtering, etc.). 

All networks are being advertised across the ethernet links and serial links. On R1, the routes (originally from R3) advertised FROM the R2 ethernet links to R1 show up as successors/feasible successors in the EIGRP topology table. The same routes advertised across the serial link between R2 & R1 only show up in the 'show ip eigrp topology all-links' table - EVEN though the RD is LESS than the FD. To my knowledge,  when the reported distance is LESS than the feasible distance = feasibility condition met! So, these routes should be in the topology table as feasible successors.

Below is a sample from the topology table and the same network from the all-links table:

topology table:
P 13.13.13.0/29, 2 successors, FD is 156416
via 10.0.1.2 (156416/130816), GigabitEthernet0/0
via 10.0.2.2 (156416/130816), GigabitEthernet0/1

toplogy all-links table
P 13.13.13.0/29, 2 successors, FD is 156416, serno 664
via 10.0.1.2 (156416/130816), GigabitEthernet0/0
via 10.0.2.2 (156416/130816), GigabitEthernet0/1
via 10.0.3.2 (2309376/156416), Serial0/1/0

Am I missing something?  

Please let me know if you want to see anything else (configs, 'show' output, etc.). Thanks in advance!

[gaganissar · Accepted solution]

Output shared appears fine. I don't see anything wrong with it.

Routes in green are installed as successor for prefix 13.13.13.0/29 doing equal cost load balancing. route in red (serial interface) failed to meet the feasibility condition because its reported distance is equal and not less than the feasible distance/composite metric of 156416.

Please share if there is something else in the eigrp or RIB table that you think is incorrect.

toplogy all-links table
P 13.13.13.0/29, 2 successors, FD is 156416, serno 664
via 10.0.1.2 (156416/130816), GigabitEthernet0/0
via 10.0.2.2 (156416/130816), GigabitEthernet0/1
via 10.0.3.2 (2309376/156416), Serial0/1/0

[#3 · Accepted solution]

toplogy all-links table
P 13.13.13.0/29, 2 successors, FD is 156416, serno 664
via 10.0.1.2 (156416/130816), GigabitEthernet0/0
via 10.0.2.2 (156416/130816), GigabitEthernet0/1
via 10.0.3.2 (2309376/156416), Serial0/1/0

[mmanthe]

THANK YOU!!

Sometimes it just takes another set of eyes ;-)

The sad part is - I KNEW that (that 'equal' also failed feasibility condition) but I was looking at it the wrong way. I was looking at the calculated FD for that individual advertisement (as calculated across the 2 serial hops) - not the overall FD. Thanks for the kick in the head - I really did need it!

[gaganissar]

I am glad I was able to assist. Yeah, sometimes comparing those values can be confusing.