EIGRP

[gowdakssujan]

Are EIGRP Hello packets unreliable(doesn't require ACK)?

[Hector Gustavo Serrano Gutierrez]

Hi @gowdakssujan,

The reception of EIGRP Hello packets (Multicast pkts destined to 224.0.0.10) does not generate any kind of ACK packet as a response.

Cheers.

[alex.perkins1]

Hello gowdakssujan,

EIGRP actually uses a protocol called RTP (Reliable Transport Protocol), not to be confused with the VoIP related RTP (Real-time Transport Protocol). Here's a really good write up of it in much more depth than I could explain here:

https://packetlife.net/blog/2009/jan/17/rtp-eigrp/

[Giuseppe Larosa]

Hello gowdakkssujan,

EIGRP Hellos are sent to multicast address by default and they are not acknowledged.

They are used to build and maintain EIGRP neighborships.

Other packet types like Query, Reply, SIA Query, SIA Reply and Update are acknowledged.

Actually an EIGRP ACK is similar to an EIGRP hello with the added field of the Ack sequence number and it has a unicast destination.

EIGRP requires that all neighbors receive all updates in an ordered manner.

In a working network the packets in queue column Q in show ip eigrp neighbors should be zero for all neighbors

Hope to help

Giuseppe