Enhanced Interior Gateway Routing Protocol

1 - four key technologies

neighbor discovery/recovery, reliable transport protocol (RTP), DUAL finite-state machine, and protocol-dependent modules.

2 - four fundamental concepts

neighbor tables, topology tables, route states, and route tagging.

3- two route states

active or passive.

4 - route tagging

Internal routes originate within an EIGRP AS.

5 - five EIGRP packet types

hello , acknowledgment, update,  query and reply.