What command in configuration mode will enable the VLAN interface if it is not already enabled?
The correct answer is B) no shutdown. To enable the VLAN interface, the correct command to use in configuration mode is "no shutdown."
Explanation:
In configuration mode, the "no shutdown" command is used to enable a VLAN interface if it is not already enabled. This command removes the administrative shutdown state from the interface, allowing it to become operational and start passing traffic. By issuing the "no shutdown" command, the VLAN interface is activated and ready to function.
The other options listed have different purposes:
A) The "ip address" command is used to assign an IP address and subnet mask to the interface.
C) The "ip default-gateway" command sets the default gateway for the device.
D) The "ip name-server" command configures DNS name servers for hostname resolution.
Therefore, to enable the VLAN interface, the correct command to use in configuration mode is "no shutdown."