Cisco Certified Network Professional Practice Test 2025 – Your All-in-One Guide to Exam Success!

The command that allows specific VLANs over a trunk link is correctly represented as "switch trunk allowed VLAN x-y, z." This command is used in Cisco devices to configure a trunk port to permit only designated VLANs to pass through the trunk link.

When configuring trunk ports, it is important to control which VLANs are allowed, as this helps limit broadcast traffic and enhances overall network efficiency. The syntax clearly specifies the allowed VLAN range (x-y) and individual VLANs (z) that can traverse the trunk link. For example, "switch trunk allowed VLAN 10-20, 30" would configure the trunk to allow VLANs 10 through 20, as well as VLAN 30.

The other commands do not utilize the correct syntax or are not applicable for this purpose in the context of Cisco command-line interface (CLI) configuration. For instance, "switch trunk allowed x-y, z" lacks the keyword "VLAN," making it invalid. Similarly, "switchport allowed VLAN x-y" does not use the correct context for trunking, and "set trunk VLAN x-y, z" is not a recognized command format in Cisco's configuration for trunking VLANs. Understanding the correct command is critical for network configurations involving VLAN