Cisco CCNA (200-301)Network AccessMedium
A network technician is troubleshooting a newly deployed wireless network. Clients are unable to connect to the SSID 'CorpNet'. The WLC GUI shows that the 'CorpNet' WLAN is mapped to VLAN 10. A 'show interface trunk' command on the switch connected to the WLC shows that VLAN 10 is missing from the allowed VLAN list on the trunk port. Which of the following commands, executed on the switch's trunk interface connected to the WLC, will resolve the issue and allow clients to connect?
- Aswitchport trunk allowed vlan add 10
- Bswitchport access vlan 10
- Cswitchport mode access
- Dswitchport trunk native vlan 10
Show answer & explanationAnswer & explanation
Correct answer: A. switchport trunk allowed vlan add 10
The issue states that VLAN 10 is missing from the allowed VLAN list on the trunk. The 'switchport trunk allowed vlan add 10' command will add VLAN 10 to the existing list of allowed VLANs on the trunk, enabling client traffic for 'CorpNet' to pass through.
Why the other options are wrong
- B. This command configures the port as an access port for VLAN 10, not a trunk port allowing multiple VLANs.
- C. This command changes the port to an access port, which would prevent other VLANs from traversing the link.
- D. This command sets the native VLAN, which is for untagged traffic, not for allowing tagged client VLANs.
Trunk Allowed VLAN Add
The 'switchport trunk allowed vlan add <VLAN-ID>' command is used on a Cisco switch to append a specific VLAN to the existing list of VLANs permitted to traverse a trunk link.
- Does not overwrite existing allowed VLANs.
- Useful for incrementally adding VLANs to an active trunk.
- Ensures new VLANs can pass through.
Memory trick: A.D.D. V. - Add Dynamic Data VLAN