Enhanced Interior Gateway Routing Protocol

aliases:

• EIGRP

A distance-vector dynamic routing protocol.

Unlike RIP, EIGRP uses two main metrics: a set of administrator-weighted elements, usually either bandwidth or delay, where:

• bandwidth is a cost value based on the lowest bandwidth link on the path
• delay is a cost value based on the latency or time it takes for a packet to traverse the link

EIGRP only sends a full update once - when it first establishes contact with a neighboring router. After that, all updates are results of network topology changes. This is more efficient and less disruptive to larger networks. Even so, EIGRP still sends regular "hello" pings to it's neighbors to ensure connectivity.

EIGRP also has a larger routing table capacity, supporting up to 255 network hops. EIGRP packets are wrapped directly in IP datagrams, not having to rely on TCP or UDP. The packets are tagged with protocol number 88 in the IP header. Updates are propagated across the network using multicast addressing.