EIGRP operations can be classified into three different categories:
The first type of operation is the network-discovery operation, which is when a router sends out a packet and waits for an ACK from the target. The network-discovery operation is used to find new entries in an EIGRP topology table.
The second type of operation is the update and query operations, where a router will send out updates and queries in order to maintain its topology table.
Finally, the third type of EIGRP operations are the active operations, which are when a router sends out queries to get information about link changes or changes in metrics with its neighbors.