When an adjacency is formed, neighbouring EIGRP routers exchange their entire routing table, following exchanges only contain partial updates as the topology changes in the network.
EIGRP uses five different types of packets to communicate with other routers, with it’s own IP number – 88.
| Type | Packet Name | Function |
| 1 | Hello | Discovering EIGRP neighbour and checking if a neighbour is no longer available. |
| 2 | Request | Used to get specific information from one or more neighbours |
| 3 | Update | Used to transmit routing or reachability information to other EIGRP neighbours |
| 4 | Query | Sent out to search for alternative paths during convergence |
| 5 | Reply | Sent in response to the query packet type |
Multicast packets are used where possible for communication between routers with the address 224.0.0.10 or unicast when required.
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