Cisco RVS4000v2 router ports tagged, untagged and with VLAN trunking

[georgedone]

I'm helping a friend to integrate a Cisco RVS4000 v2 (donation) into a small network.
The network contains a TP-Link managed switch, VLAN capable, 2 OpenWRT routers, some PC's, printers, Synology NAS and a few servers (FreeBSD and Windows).
The Cisco RVS4000 v2 router was updated to the latest firmware available (2.0.3.4). It supports up to 4 VLANs and when a port is placed in a VLAN will need to be declared as "untagged", "tagged" or "trunk". When configured as a trunk a default PVID has to be configured. Trunk is here used in Cisco terminology (related to VLANs, no LACP or other Ethernet bonding meaning). I kind of understand what each of the three options does to ingress and egress frames respectively. What I need help to understand is the typical use for each scenario.
For instance, an untagged port will be connected to a printer, a PC or other device which does not understand VLANS. A tagged port will be connected to a switch or router understanding VLANs, or to a server/NAS whose network interface was configured with VLAN support. But in which scenario I would need a port to be configured as a trunk ? From the Cisco documentation I understood the trunk port would pass tagged frames with the exception of the PVID, on the egress the VLANid would be removed from the frame if it matches PVID and on the ingress it would be added to the frame if the frame was untagged previously. If the frame was tagged with a different VLANid it will be transmitted as such.

 

[coxhaus]

You use a trunk port to pass multiple tagged VLANs.

You will want to use the TP-Link managed switch for the VLANs. It will be faster. Use the router to add layer 3 IP addressing and routing.

I am assuming your switch does not have DHCP support otherwise use the switch. I would look at setting up the VLANs on the router for DHCP, setting each VLAN as a separate IP network.. Create a trunk on the router to connect to the switch on a trunk port. Setup the VLANs on the switch to match the trunk VLANs. This is the way I setup VLANs where every VLAN has an IP network address. I think it works best.