EIGRP Algorithm

eng_ahmedas

Dear Friends
I wish u r all in very good health.i have 2 questions concerning EIGRP.
First: Does an EIGRP router includes a list of all routes advertised by neighbors or includes only successors routes and routes from neighbors who achieve the fesabile condition.

Second: Is it true that FD changes only during an active-to-passive transition,[i.e. if a successor of FD 20 goes down , so the Fesible successor of total cost 25 be successor, will the FD change to 25 or remians 20 until the route change from passive to active ???]

Thanks in advance
bye

EdTheLad

eng_ahmedas wrote:

Dear Friends
I wish u r all in very good health.i have 2 questions concerning EIGRP.
First: Does an EIGRP router includes a list of all routes advertised by neighbors or includes only successors routes and routes from neighbors who achieve the fesabile condition.

The topology table will contain all routes advertised by neighbors as long as the routes
adhere to the split-horizon rule.Only the successor is placed in the routing table or multiple successors load sharing.
In the topology table you can see only the successors and feasible successoe if you type
"show ip eigrp topology" if you type "show ip eigrp topology all" you will see even routes that have a AD > FD .

eng_ahmedas wrote:

Second: Is it true that FD changes only during an active-to-passive transition,[i.e. if a successor of FD 20 goes down , so the Fesible successor of total cost 25 be successor, will the FD change to 25 or remians 20 until the route change from passive to active ???]

The FD will remain at 20,if there is no feasible successor the route will go active and the FD will be modified to the newly discovered value.
In your senario if a new neighbor was connected with a FD 15 less than the current successor 20, the new neighbor would become the successor and the FD would be modified to 15,updates would then be sent to all neighbors.
So as you can see the FD can be modified during an active-to-passive transition and also if a new FS appears with a lower cost than the current successor.