Packet types (Message types)

Packet types (Message types).

There are 5 packet types.

• Hello
• Update
• Query
• Reply
• Ack

1 - Hello - Used to discover EIGRP neighbors

• Sent out every 5 seconds on all links except multi-access links slower then 1.544 Mbps
• On those links we send out hello every 30 seconds.
• Sent using 224.0.0.10 and FF02::A multicast group for IPv4 and IPv6 EIGRP respectively. The L2 multicast address start with 01:00:5e:00:00:0a. The last half of the multicast address (00:00:0a) is derivative of the multicast IPv4 address.
• Hold timer is 3x the hello interval.

EIGRP Hello snip from Wireshark.

2 - Update (Acknowledged).

This is how we share new routing information and are triggered, which means that something happened. 

3 - Query (Acknowledged)

Sent when the successor fails and there is no feasible successor.

4 - Reply (Acknowledged)

This is a response to a query.

5 - Acknowledgement

The Ack number matches the sequence umber of the packet being acknowledged. In the below example the value is 35 which indicated that the packet received had the same value for the sequence number.

Ack is sent for Updates, Queries and Replies.