CCNA Data Center DCICN 640-911 Official Cert Guide

EIGRP Maintains Neighbor Status Using Hello

Unlike RIP, EIGRP does not send full or partial update messages based on a periodic timer. When a router first comes up, it advertises known routing information. Then, over time, as facts change, the router simply reacts, sending partial updates with the new information.

The fact that EIGRP does not send routing information on a short periodic timed basis greatly reduces EIGRP overhead traffic, but it also means that EIGRP cannot rely on these updates to monitor the state of neighboring routers. Instead, EIGRP defines the concept of a neighbor relationship, using EIGRP hello messages to monitor that relationship. The EIGRP hello message and protocol defines that each router should send a periodic hello ...