Exchanging EIGRP Topology Information

EIGRP exchanges topology information between routers using a variety of messages called EIGRP packets. These packets contain the following types of information:

Hello Packets: These packets are used to discover EIGRP neighbors on a network segment. They are sent periodically by each router, and contain information about the sending router’s EIGRP configuration, including its AS number and K-values.

Update Packets: These packets are used to update other routers about changes in the network topology. They contain information about the destination networks, their metrics, and the next-hop routers.

Acknowledgment Packets: These packets are sent in response to received Update packets to confirm that they have been received.

Query Packets: These packets are sent by a router when it needs information about a particular destination network. They are broadcast to all routers in the EIGRP domain, and other routers respond with information about the destination network.

Reply Packets: These packets are sent by a router in response to a Query packet, and contain information about the destination network.

EIGRP also maintains a topology table, which contains information about all the networks in the EIGRP domain, their metrics, and the next-hop routers. This information is used by EIGRP to calculate the best path to each destination network. EIGRP uses a metric that takes into account factors such as bandwidth, delay, reliability, load, and MTU. The metric can be configured using various parameters such as the bandwidth and delay of the link, and the minimum and maximum bandwidth values. EIGRP also supports load balancing across multiple paths, which can improve network performance and redundancy.