EIGRP-Operation, Terminology and Planning

EIGRP Maintains three tables:

• Neighbour Table – Directly Connected Routers/List of Adjacent Routers.
• Topology Table – Lists all the Learned routes to each destination.
• Routing Table – Contains best Rote to each Destination (Successor)

EIGRP Terminology:

• Feasible Distance (FD)- Total metric along a path to a destination network advertised by an upstream neighbor.
• Advertised Distance(AD)-is the distance from a given neighbor to the destination router.
• Successor-Primary Route. Installed in the routing table.
• Feasible Successor-Backup Route. Installed in Topology Table. (To be a Feasible Successor, the AD must be less than the FD of the successor).
• Passive Interface-Keeping a passive interface prevents a neighbor relationship from being established over a passive interface. 
• Stuck-In-Active- when a route goes active and queries are initiated, the only way this route can come out of the active state and transition to passive state is by receiving a reply for every generated query. If the router does not receive a reply to all the outstanding queries within 3 minutes (the default time), the route goes to the SIA state.

Route Status:

            Active-Bad Route.

            Passive-Good Route.

EIGRP Implementation Plan:

• The IP addresses to be configured on individual router interfaces.
• The EIGRP autonomous system number, used to enable EIGRP. The autonomous system number must be the same on all the routers in the EIGRP domain.
• A list of routers on which EIGRP is to be enabled along with the connected networks that are to run EIGRP and that need to be advertised (per individual router).
• Metrics that need to be applied to specific interfaces, for EIGRP traffic engineering. The required metric and the interface where the metric needs to be applied should be specified.

EIGRP Verification Commands:

Neighborship

show ip eigrp neighbors

show ip eigrp neighbors details

Routes

show ip route

show ip route eigrp

show ip protocols

show ip eigrp interfaces

show ip eigrp topology

show ip eigrp traffic

Debug Commands

debug eigrp packets

debug ip eigrp

debug ip eigrp summary
debug eigrp neighbors