Any interface that you assign to a trunk must be an untagged interface. Furthermore, you can assign an interface to one trunk only; that is, you cannot assign the same interface to multiple trunks.
Because of these restrictions, the only interfaces that appear in the Interfaces list in the BIG-IP® Configuration utility are untagged interfaces that are not assigned to
another trunk. Therefore, before creating a trunk and assigning any interfaces to the trunk, you
should verify that each interface for the trunk is an untagged interface.