EIGRP Finate State Machine

[rd1hamdaoui1]

Hi EveryOne, 

If a router goes active for a destination, and if before it receives all its replies it detectes a delay increase for the same network it goes active for, the router will wait to receive all its replies, and then check if the best received reply respect the Feasibility Condition.

I'm wondering why this Feasiblity Condition Check against the best received Reply?

[Martin L]

It cannot do that; Rules says: when DUAL goes into Active for net X, router cannot:

-change distance for x

-change route's successor nor change FD

-start another DUAL calculations for route Y

Regards, ML
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[rd1hamdaoui1]

Thanks for your reply,

but when the router first goes active it puts itself in the A3 (Successor Origin) or A1 (Local Origin) active states,and if another distance increase is detected the router change the state from A3 to A2 (Multiple Origins), or from A1 (Local Origin) to A0.

The router waits to receive all remaining Replies. When the last Reply arrives, The router will first check whether the neighbor providing the least Computed Distance passes the Feasible Condition check using the Feasibility Distance value set when the route entered the Active state.

im wondering why this check of the Feasibility Condition on the best received reply?

[Martin L]

I will have to review TCP.IP book; i think there is example my help. meanwhile please review following posts

see https://community.cisco.com/t5/routing/definition-of-feasible-distance-in-eigrp-convergence/m-p/4087265#M334424

then https://community.cisco.com/t5/routing/eigrp-why-is-the-fd-a-historical-record-for-fastethernet-but-not/m-p/4088936#M334580