Refer to the exhibit. It is desired to set up a BGP neighbor relationship between routers R1
and R4. BGP packets between them could travel through R2 or R3. What is the simplest
configuration that will allow for failover? Select the best response

A.
Configure BGP neighbor relationships between all interfaces on R1 and R4.

B.
Install a direct connection between R1 and R4.

C.
Configure loopback interfaces on R1 and R4 to provide the update source address for
BGP packets.

D.
Configure only one neighbor relationship between R1’s 192.168.1.2 interface and R4’s
172.16.10.2 interface.

Explanation:
The point of this question is about using lookback interface establish neighbor.
You can use two ways to configure IBGP neighbor. First is use physical address, and the
second is use loopback interface. In this picture, you find that there are two way to each
other, if you use physical address for failover, you need to establish two connection, and you
will receive two route, this is no good. If you use loopback interface, there are only one
connection, but if one way is down, it also can failover. So answer B is the best.