Troubleshooting EIGRP
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Each router establishes a neighbor table, in which it stores important
information regarding the neighbors that are directly connected. The infor-
mation consists of the neighbor's IP address, hold time interval, smooth
round-trip timer (SRTT), and queue information. These data are used to
help determine when the link state changes.
When two routers initialize communication, their entire route tables are
shared. Thereafter, only changes to the route table are propagated. These
changes are shared with all directly connected EIGRP-speaking routers.
Each of these steps is summarized below.
1.
Hello packets are multicast out all of the router's interfaces.
2.
Replies to the Hello packets include all routes in the neighbor router's
topology database, including the metrics. Routes that are learned from
the originating router are not included in the reply.
3.
The originating router acknowledges the update to each neighbor via
an ACK packet.
4.
The topology database is then updated with the newly received infor-
mation.
5.
Once the topology database is updated, the originating router then
advertises its entire table to all the new neighbors.
6.
Neighbor routers acknowledge the receipt of the route information
from the originating router by sending back an ACK packet.
These steps are used in the initialization of EIGRP neighbors and change
somewhat only when updates are sent to existing neighbors.
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