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/0/0/0 interface 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 stub command.

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.
If we use the passive-interface command on s0/0/0 interface then router A & B can not become
neighbors because they don’t exchange hello messages -> A can not send traffic to the network
behind B .
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.
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.