Question

Two switches, SW1 and SW2, are connected by an 802.1Q trunk. Users in VLAN 1 on both switches can communicate, but the switch logs on SW1 repeatedly display: '%CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet0/1 (99), with SW2 GigabitEthernet0/1 (1).' Untagged management traffic is also behaving unexpectedly. What is the most likely cause and correct action?

Accepted Answer

The native VLAN is configured as 99 on SW1 and 1 on SW2; set both trunk ports to the same native VLAN.

Answer

The trunk encapsulation differs between switches; configure ISL on both ends to match.

Answer

VLAN 99 has not been created in the VLAN database; create VLAN 99 on both switches to clear the message.

Answer

The allowed VLAN list is pruning VLAN 1; add VLAN 1 to the allowed list on both trunk ports.