EIGRP messaging

Had a couple questions about EIGRP and the various messages that it sends out. Below is my current understanding and some questions that I have. Someone please correct me if I am wrong.

Hello packets - Sent out when EIGRP protocol is first activated to discover neighbors. Also sends periodic Hello through multicasting to detect new neighbors or neighbors that have become unreachable. The time period that a router should recieve a hello packet from its neighbors are found in the neighbor table of the router. As long as the router keeps recieving hello packets from its neighbors he can send and recieve routing information.

WHY CAN'T I SEE HELLO PACKETS BEING TRANSMITTED WHEN I DEBUG EIGRP?

IS THE TIMER OF HOW OFTEN A ROUTER SENDS A HELLO PACKET AUTOMATED OR CAN IT BE SENT MANUALLY? HOW IS IT DETERMINED HOW OFTEN TO SEND A HELLO PACKET?

Update packets - Requires reliable transfer using RTP and requires an ACK packet from the neighbor confirming that it was recieved. Update packets are used when the hello packet discovers a new neighbor. The entire topology table is sent to this neighbor using the update packet as a unicast. Update packets are also used when the link-cost changes in a router via a multicast.

WOULD THIS BE WHENEVER THE TYPE OF METRIC CHANGES OR THE CURRENT METRIC CHANGES VALUES?

Queries and Replies - These are sent when the router goes into active state because there are not feasiable successors in the topology table and it has to ask the router for an alternate route. The Reply is the neighboring routers answer to the query.

Thanks in advance[/b]

Find more posts tagged with

Comments

darkuser

http://www.cisco.com/en/US/products/sw/iosswrel/ps1828/products_configuration_guide_chapter09186a00800ca56e.html#wp4822

gojericho0

Since the hello interval can be changed does the time period to recieve a hello have to be the same for the routers to be seen as a neighbor? I am thinking that the hello time period would not matter just as long as the hello is recieved before the clock hits 0 since they are directly connected.

Thanks again

tunerX

Identical holdtimes are not a requirement. You can have different hello times. It will really mess up convergence if one side sees a neighbor as down and the other side sees a neighbor as active.

Yankee

if the timers are different on two neighbors, eigrp will use the quicker timers.

Yankee