EIGRP question

When a new router is added to an EIGRP routing protocol enviroment and has the same autonomous system number will it broadcast its signal to out all interfaces to discover neighbors than change to multicast and periodically send hellos to all routers that acknowldged its presence?

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Comments

johnnynodough

It will do everything via multicast, identify neighbors and exchanges. Same as RIP V2 and OSPF. The routing protocol interfaces will recieve packets at the multicast address 224.0.0.10,All interfaces that have been enabled for EIGRP with a network command.

gojericho0

Ok gotcha so any network I add using the network command will recieve a multicast and continue to recieve the multicast as long is nothing changes?

johnnynodough

Yep.

Yankee

Not to muddy the waters but there are some functions where EIGRP uses a unicast to communicate with a neighbor, but that may be more than ya need to know.

Yankee

johnnynodough

Dangit Yankee! Now I am going to have to read up on that

Even if something is beyong the scope of the CCNA, if it intrigues me I must learn about it to appease my feeble mind

darkuser

he's right

you can use a unicast your eigrp processes.

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fipr_c/ipcprt2/1cfeigrp.htm

ever heard of an eigrp goodbye message ?

normally there are also cases in ripv2 where using a neighbor statement and passive-interface works, unless you're not allowed then
you have to do that with an access-list and nat. (black-magic)

gojericho0

Ok one more question. EIGRP gets routing info from its neighbors just like a distance vector protocol but it still can see the whole network because of the topology table, so why doesn't it just use link-state like OSPF and find out for itself the cost of the network instead of relying on it's neighbors?