EIGRP Successor question.

waru

Hi,

As I understand it, upto 4 feasible successors for any route can be held at one time in the topoogy table. However in some places I have read there can also be upto 4 successors in the routing table? Surely that is incorrect and there is only ever 1 successor for any route held in the routing table at any one time?

Cheers,
Waru

Paul Boz

There can be up to four feasible successors in the topology table, but only one actual successor route in the routing table. The routing table is the "cream of the crop" routes, so only one exists. If the successor route dies, EIGRP selects the best feasible successor from the topology table and injects it into the routing table, replacing the dead successor route.

dtlokee

There can be up to 4 equal cost paths to a destionation (by default) which would indicate there can be 4 successor routes in th routing table (you can configure EIGRP to allow 6 with the maximum-paths command). By definition a "feasible successor" is the router with the lowest advertised distance (AD) to a destination. If the AD is the same for multiple next hop routers, they will all become the successor(s). You can also configure unequal cost load sharing for EIGRP and up to 6 paths using the variance command.

Hope this helps