Oops, I need to correct myself after reading your follow on question and your rereading your original question.
A router can have subinterfaces to allow that physical interface to act somewhat like a trunk. Unfortunately, one major difference between a router interface and a switch trunk interface, the switch allows multiple interfaces in the same VLAN while (normally) a router does not.
What I now think your original question was really asking was for a router to operate like a bridge (switch). To this question, some can, although I don't recall if they can support multiple VLAN using subinterfaces or can, while bridging a pair of router ports, support VLAN tagging.
It's been a long time since I've needed to bridge through a router. One of the past terms for this feature was IRB. You might read up on that. Hopefully, someone else, more current on this kind of technology will post a response too.
