Refer to the exhibit. ROUTE Enterprises has many stub networks in their enterprise
network, such as router B and its associated network. EIGRP is to be implemented on
router A so that neither the prefix for the S/0/0/0interface nor the prefixes from router B
appear in the routing tables for the router in the enterprise network.
Which action will accomplish this goal?

A.
Declare router B a stub router using the eigrp stubcommand.

B.
Use the passive-interface command for interface Serial0/0/0.

C.
Use a mask with the network command to exclude interface Serial0/0/0.

D.
Implement a distribute list to exclude the link prefix from the routing updates.

Explanation:
If we declare router B a stub router then the routers in Enterprise Network still learn about
the network for S0/0/0 interface and the network behind router B -> A is not correct.
If we use the passive-interface command on s0/0/0 interface then router A & B can not
become neighbor because they don’t exchange hello messages -> A can not send traffic to
the network behind B -> B is not correct.
Theoretically, we can use a distribute list to exclude both the link prefix and the prefix from
router B but it is not efficient because:
+ We have many stub networks so we will need a “long” distribute list.
+ We declare networks in stub routers (like router B) while filter them out at router A -> it is a
waste.
I am not totally sure about answer C because if we “use a mask with the network command
to exclude interface Serial0/0/0″then router A and B can not become neighbors and the
situation is same as answer B. But from many discussions about this question, maybe C is
the best answer.