If a port or port-channel receives tagged frames and untagged frames, for configured native VLANs, then all tagged and untagged frames would be processed as follows:
- All untagged frames are classified into native VLANs configured.
- Any tagged frames coming with a VLAN tag equal to the VLANs configured under port or port-channel for the command
switchport trunk allowed vlan <>, are processed.
Here is an example of a port-channel configured for tagged traffic for VLAN 100 & VLAN 101 and untagged traffic for VLAN 30:
interface Port-channel 1
switchport mode trunk
switchport trunk allowed vlan add 100-101
switchport trunk tag native-vlan
switchport trunk native-vlan 30