What is the name of the protocol that is used by EIGRP to send update messages between neighbors?

The protocol used by EIGRP to send update messages between neighbors is known as the Reliable Transport Protocol (RTP). This protocol is a crucial component of EIGRP, as it ensures that routing information is communicated efficiently and reliably between routers that are part of the same EIGRP routing domain.

RTP operates on top of IP and provides the necessary reliability for message delivery, allowing EIGRP to use both unicast and multicast delivery methods as needed. It effectively acknowledges the receipt of messages, which helps to prevent the loss of routing updates and ensures that routers maintain consistent and accurate routing tables. The reliable nature of RTP is particularly important in dynamic networks where changes can occur frequently, as it helps to keep all participating routers synchronized with the most current routing information.

The other options mentioned, such as the Enhanced Interior Gateway Routing Protocol, Exterior Gateway Protocol, and Intermediate System to Intermediate System Protocol, refer to different protocols in the context of network routing and do not focus directly on the specifics of how EIGRP manages its message updates between neighbors.