Cisco Certified Network Associate (CCNA) Practice Exam

Which command is used to encapsulate a sub-interface for Inter-VLAN configuration?

1. (config-subif)#no shut

2. (config-subif)#ip address IP ADDRESS AND SUBNET MASK

3. (config-subif)#encapsulation dot1q VLAN NUMBER

4. (config)#interface INTERFACE.SUB-INTERFACE

The correct answer is: (config-subif)#encapsulation dot1q VLAN NUMBER

The command that is used to encapsulate a sub-interface for Inter-VLAN configuration is indeed encapsulation dot1q VLAN NUMBER. This command is essential for configuring VLAN tagging on a sub-interface, which allows the router to recognize and separate traffic for different VLANs. When a router is configured to handle Inter-VLAN routing, each sub-interface needs to be created specifically for each corresponding VLAN. The “encapsulation dot1q” command applies the IEEE 802.1Q protocol to the specified VLAN number, which tags the frames with the appropriate VLAN ID. This tagging is necessary for the router to properly forward the frames to their respective VLANs and ensure that traffic is properly routed between different VLANs within the network. The use of sub-interfaces is prevalent in router-on-a-stick configurations, where a single physical interface is used to route traffic for multiple VLANs, improving resource utilization and simplifying the network architecture. By applying this encapsulation command, the router can efficiently manage VLANs within a network environment.