Implementing Cisco IP Switched Networks (SWITCH v2-0) (#528)

What occurs when an untagged frame is received by an 802.1Q trunk port?

It discards the frame.
It tags the frame with the identified native VLAN value.
It forwards the frame out each port of the switch not assigned to a VLAN.
It forwards the frame to a port belonging to the same VLAN as the native VLAN.