Which option also is required on the tunnel interface before it is operational?

An engineer is configuring a GRE tunnel interface in the default mode. The engineer has assigned an IPv4 address on the tunnel and sourced the tunnel from an Ethernet interface.

Which option also is required on the tunnel interface before it is operational?
A . (config-if)#tunnel destination <ip address>
B . (config-if)#keepalive <seconds retries>
C . (config-if)#ip mtu <value>
D . (config-if)#ip tcp adjust-mss <value>

View Answer

Answer: A

Explanation:

A GRE interface definition includes:

+ An IPv4 address on the tunnel

+ A tunnel source

+ A tunnel destination

Below is an example of how to configure a basic GRE tunnel:

interface Tunnel 0 ip address 10.10.10.1 255.255.255.0 tunnel source fa0/0 tunnel destination 172.16.0.2

In this case the “IPv4 address on the tunnel” is 10.10.10.1/24 and “sourced the tunnel from an Ethernet interface” is the command “tunnel source fa0/0”. Therefore it only needs a tunnel destination, which is 172.16.0.2.

Note: A multiple GRE (mGRE) interface does not require a tunnel destination address.