What would be the effect of changing the IP address from 0.0.0.0 to 1.2.3.4?

When configuring ISAKMP for IKEv1 Phase1 on a Cisco IOS router, an administrator needs to input the command crypto isakmp key cisco address 0.0.0.0. The administrator is not sure what the IP addressing in this command issued for.

What would be the effect of changing the IP address from 0.0.0.0 to 1.2.3.4?
A . The key server that is managing the keys for the connection will be at 1.2.3.4
B . The remote connection will only be allowed from 1.2.3.4
C . The address that will be used as the crypto validation authority
D . All IP addresses other than 1.2.3.4 will be allowed

Answer: B

Explanation:

The command crypto isakmp key cisco address 1.2.3.4 authenticates the IP address of the 1.2.3.4 peer by using the key cisco. The address of “0.0.0.0” will authenticate any address with this key