Cisco Certified Network Associate (CCNA) Practice Exam

Which command configures a Trunk link?

1. (config-if)#switchport trunk encapsulation dot1q

2. (config-if)#trunk mode enable

3. (config-if)#switchport mode access

4. (config-if)#interface trunk

The correct answer is: (config-if)#switchport trunk encapsulation dot1q

The command that configures a trunk link effectively is the one that sets the encapsulation method to IEEE 802.1Q, which is commonly used for VLAN tagging on trunk links in Cisco switches. The command you mentioned specifies the encapsulation type, indicating how the switch will package VLAN information in the frames that pass across the trunk link. When configuring trunk links, it’s crucial to specify the encapsulation method to ensure that both ends of the trunk link can communicate properly. Using 802.1Q allows for multiple VLANs to be carried over a single physical link, thereby optimizing bandwidth and reducing the number of physical connections needed between switches. Other options presented do not accurately set up a trunk link. For instance, enabling trunk mode without specifying encapsulation or defining switchport mode access does not configure the trunk properly. The command that is meant to verify and manage the overall operation of the interface does not exist in standard configuration practices (thus rendering it invalid). Therefore, for proper trunk configuration, setting the encapsulation to 802.1Q is essential.