EIGRP UPDATE

[jaighobahi]

Hi Folks,

I have issues understanding the EIGRP update process.  Attached is a word document containing screen shots from a Wireshark capture.  Please, have a look at them and offer your thought.  Thanks.

[Vasilii Mikhailovskii · Accepted solution]

Hello.

Recently Cisco published RFC draft for EIGRP, where you may find all the answers - https://www.ietf.org/id/draft-savage-eigrp-04.txt

Basically:

• section 5.3.3-4 says about INIT-flag to start initial update process (NULL INIT-packet);
• next-hop is 0.0.0.0 - means we use neighbour IP-address as next-hop (as we may announce some other attached IP-address as next-hop);
• unicast update retransmit may come,as 192.168.1.2 has not acknowledged multicast update (in this case we switch to unicast mode). 

PS1: I would suggest you to test EIGRP on 15.2+ release, as draft is most probably covers latest version.

PS2: if you repeat the test with 15.2+ release, please attach pcap file along with your questions.

[jaighobahi]

Thanks a lot.  The link is very helpful.