eigrp, good bye message

[sarahr202]

Hi everybody.

Let say we have two routers, r1 and r2 , both understand " good bye" message if for any reason they have to drop adjacency they can send " good bye" message and drop the adjacency.

Now what if we have two routers say r3 and r4. r3 is a new router and therefore understands " good bye " message, while r4 does not.

r3--------------r4.

Let say both routers above have formed adjacency. Suppose for some reason, r3 has to drop the adjacency, r3 therefore crafts a " good bye" message (i.e all k,svalues set to 255).  How will r4 react upon receiving this goodbye message?  Will r4 drop the adjacency? or will r4 continue to wait until hold timer expires and then drop the adjacency?

thanks and have a great day.

[Raju Sekharan · Accepted solution]

It will drop the session reporting K-Value mismatch has below

 *Apr 26 13:48:41.811: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor     10.1.1.1 
(Ethernet0/0) is down: K-value mismatch

Reference link:

http://www.cisco.com/en/US/docs/ios/12_2/ip/configuration/guide/1cfeigrp.html

Thanks

Raju

[sarahr202]

Hi Raju.

Thanks for your response and great link.  However I just found out from your link( as quoted below) the non supporting peer will not drop adjacency rather it will wait for hold timer to expire and then drop adjacency.

The receipt of a goodbye message by a nonsupporting peer does not disrupt normal network operation. The nonsupporting peer will terminate session when the hold timer expires. The sending and receiving routers will reconverge normally after the sender reloads

Thanks and have a great day.

[Raju Sekharan · Accepted solution]

You are welocome

I tried it in 12.2(18)SXF9 image.

1. I went to the neighbor R2 and shut eigrp process there

R1 immedaitely received K-value mismatch error and the neighborship went down

R1#sh ip eigrp nei

IP-EIGRP neighbors for process 1

H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq

                                            (sec)         (ms)       Cnt Num

0   192.168.12.2            Et0/0            161 00:01:28   53   318  0  28

R1#

00:19:32: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 192.168.12.2 (Ethernet0/0) is down: K-value mismatch

R1#sh ip eigrp nei

IP-EIGRP neighbors for process 1

R1#

00:19:56: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 192.168.12.2 (Ethernet0/0) is up: new adjacency

2. When I reload the neighbour router, the neighbor relation is going down only after hold-down timer expiry

Wish you a good day

Raju

[sarahr202]

Thanks Raju