I just have an inquiry about the EIGRP topology table. I'm trying to filter routes from our one of our site. Here's the initial EIGRP topolgy table before applying the prefix-list blocking 10.0.0.0/8 prefix.
At first, the primary route is via ATM1/0.308 and other routes are via other ATM.
After applying the prefix-list and distribute-list that block 10.0.0.0/8 network in ATM1/0.308, the primary route became Fa0/0
I understand that Fa0/0 has the best metric to 10.0.0.0/8 after applying the configuration but why did it not appear in the topology table prior to applying the distribute list.
I also understand that Reported Distance should be lower than the Feasible Distance to become a Feasible successor but why is it that routes to ATM1/0.105 and ATM1/0.106 is in the topology table prior to the prefix-list and distribute list configuration. The reported distance of those routes are 2516992 which is greater than the ATM1/0.308's 2514432. So it did not become an FS. But why is it that the route to Fa0/0 is not there where 2517248 is also greater than the Successor metric.
We do not know enough about the topology of your network to be sure. But I wonder if the neighbor at 10.199.32.2 on the Fa0/0 interface was learning the route to 10.0.0.0/8 from this router before the distribute list was applied. If so then split horizon would prevent advertising that route back on the Fa0/0 interface. After the distribute list is applied then the neighbor is no longer learning the route from this router and is able to advertise the route over the Fa0/0 interface. Perhaps you can remove the distribute list and then check on 10.199.32.2 to see how and where it is learning the route?