Examkin

Question

Difficulty: HardAP and WLC Management Access Connections

A network engineer connects a Cisco Lightweight Access Point (AP) to an 802.1Q trunk interface on a Layer 2 access switch. The AP is intended to join a Wireless LAN Controller (WLC) via its management interface using untagged CAPWAP control traffic. The switch port is configured with switchport mode trunkswitchport\ mode\ trunk and switchport trunk native vlan 50switchport\ trunk\ native\ vlan\ 50. However, the AP fails to establish a CAPWAP tunnel, and syslog messages on the switch indicate native VLAN mismatch errors. CDP neighbor outputs confirm that the switch expects tagged traffic on VLAN 1 while transmitting native frames on VLAN 50. Which switchport configuration change correctly resolves the AP's management access failure while allowing untagged CAPWAP discovery traffic?

  1. Reconfigure the switchport native VLAN to match the untagged subnet VLAN assigned for AP management access.Answer
  2. B
    Enable spanning-tree portfast directly on the switch trunk port to override the native VLAN mismatch detection mechanism.
  3. C
    Modify the CDP timer parameters on the switch interface to force the AP to dynamically adjust its management VLAN ID based on CDP TLV metadata.
  4. D
    Change the WLC management interface configuration to send untagged frames exclusively across the dedicated out-of-band Service Port.

Answer

Reconfiguring the switchport native VLAN to match the untagged subnet VLAN assigned for AP management access correctly resolves the management connectivity failure.
Lightweight Cisco APs transmit untagged packets for CAPWAP management discovery by default. If the switchport connected to the AP is an 802.1Q trunk, untagged traffic is placed into the trunk's configured native VLAN. When the native VLAN on the switch port does not match the actual IP subnet dedicated to AP management, the AP cannot communicate with the gateway or reach the WLC management interface. Reconfiguring the switch port's native VLAN to match the AP management subnet resolves the tagging mismatch and restores CAPWAP connectivity.

Step-by-Step Solution

1
Identify the cause of the CAPWAP discovery and management access failure.
Lightweight APs send untagged management/CAPWAP frames by default during initial discovery unless explicitly configured with a management VLAN tag.
When the connected switch port uses a native VLAN (VLAN 50) that differs from the subnet broadcast domain expecting untagged AP traffic (VLAN 1), 802.1Q native VLAN mismatch occurs and traffic drops.
2
Evaluate the switchport 802.1Q trunking behavior.
Changing the switchport native VLAN setting (switchport trunk native vlan <vlan−id>switchport\ trunk\ native\ vlan\ <vlan-id>) to match the AP's untagged management network allows untagged CAPWAP packets to enter the correct Layer 2 domain.
Matching the native VLAN on both ends of an 802.1Q trunk allows untagged AP control frames to reach the default gateway and route to the WLC management interface.

Key Concept

AP and WLC Management Switchport 802.1Q Native VLAN Alignment
Estimated Time:2m 0s
Rate this question

Topics

AP and WLC Management Access Connections

More questions from this topic