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best book for ccna 200 301.EIGRP sends topology information to its neighbors with an EIGRP UpdateMessage. If the sending router needs to update multiple routers in the same subnet, then that router can send these update messages to the multicast IP address 224.0.0.10; otherwise, the update messages are sent to the unicast IP address of a specific neighbor (Hello messages are always sent to the multicast IP address 224.0.0.10) but in the LANallows EIGRP to use multicast packets to efficiently exchange routing information with all neighbors in the LAN.Update messages are sent using the Reliable Transport Protocol (RTP). Similar to OSPF, the important role of RTP is that EIGRP resends routing updates that were lost in transit. By using RTP, EIGRP can better avoid loopbacks. because the router knows explicitly that the neighboring router has received the updated routing information. (Basic DV protocols like RIP do not have any mechanism to know if an update message has been received by an adjacent router, and the use of RTP is nothing more than a basic DV protocol196 Chapter 9 understanding of the differences between the EIGRP concept and the more advanced EIGRP is just another example.) Tip: The acronym RTP also refers to a different protocol, the Real-time Transport Protocol (RTP), which is used to transport voice and video IP packets.Neighbors use both full routing updates and local routing updates. A full routing update means that the router sends information about all known routes, while a local routing update includes information about only the most recently changed routes. When a neighbor first appears, full routing updates are used. After that, the neighbor reacts to the routing change by sending only local routing updates.Figure 9-9 shows the entire process from discovering neighbors using Hello messages, to sending full routing updates, continuously sending Hello messages to maintain neighbor relationships, and local routing updates, from top to bottom.Neighbor Discovery (Hello) Neighbor Discovery (Hello)Complete Routing Update I ~> Complete Routing UpdateContinuous Hello Continuous Hello ----------.Partial update (state change and new subnet information) Partial update (state change and new subnet information)