[fusion_text]EIGRP is a classless routing protocol, meaning that it sends the subnet mask of its interfaces in routing updates, which use a complex metric based on bandwidth and delay

– It Supports VLSM and discontiguous networks
– Use Reliable Transport Protocol (RTP) to delivery and reception of EIGRP packets
– Use the best path selection Diffusing Update Algorithm and  guarantees loop-free paths and backup paths in the routing domain.
– Send hello messages to discover and monitor connection status with its neighbors.
– Exchanges full routing table at startup and sends partial triggered updates (only to routers who needs this information). (Distance-Vector uses full updates).
– Supports IPv4, IPv6, AppleTalk and IPX/SPX networks.
– Support unequal metric load balancing.

EIGRP uses five types of packets to communicate to each other:
Hello: used to identify neighbors. They are sent as periodic multicasts
Update: used to advertise routes, only sent as multicasts when something is changed
Ack: acknowledges receipt of an update. In fact, Ack is Hello packet without data. It is always unicast and uses UDP.
Query: used to find alternate paths when all paths to a destination have failed
Reply: is sent in response to query packets to instruct the originator not to recompute the route because feasible successors exist. Reply packets are always unicast to the originator of the query[/fusion_text][separator style_type=”none” top_margin=”5″ bottom_margin=”” sep_color=”” border_size=”” icon=”” icon_circle=”” icon_circle_color=”” width=”” alignment=”center” class=”” id=””]