3.5 EIGRP [for IPv4 and IPv6]

3.5.a Describe packet types

3.5.a [i] Packet types [hello, query, update, and such]

EIGRP Packet Types:

Hello: used to establish neighborship

Update: used to update routing information

Query: used to ask for routing information

Reply: used to reply to queries

Ack: acknowledges reliable packets

Note: Update, Query and Reply require Ack’s

EIGRP uses the mulitcast address 224.0.0.10 for the exchange of hello’s, and the AS numbers must match. On broadcast, multipoint, point-to-point serial and point-to-point subinterface links greater than T1 speed, Hellos are sent every 5 seconds. For slower links hellos are sent every 60 seconds. The hold-time is three times the hello value. Unlike OSPF, these setting do not have to match.

Update, query and reply packets require acknowledgement, whereas hello and ack do not require ack.

Neighborship reset occurs after a 16 retry limit is reached. Slow neighbors will be sent unicast updates instead.