VLAN using OpenWrt as switch / dumb ap

I have a question of understandig when using OpenWrt as dump ap with integrated VLAN switch.

When using a cheap unmanaged switch all packets, regardless if they were tagged or they where untagged are bypassing the switch.
This switch in the ground floor has a connection to an other unmanaged switch in the first floor.
That is fine so far, since I have a single cable from the basement and I want to have all data in the ground floor and the first floor too.

I have connected dump ap's (WDR4900) to this unmanged switches. They are using 2 VLAN's (set to tagged an the WAN port).
All other devices don't care about VLAN and are using the untagged data.
Works without any problems.

Since the WDR4900 has 4 unused LAN ports and a VLAN switch, I was wondering if it is possible to remove the unmanaged switches.
The idea is to set LAN port 4 like WAN port and "bridge" them together, and LAN 1-3 as untagged ports.
So I can use WAN as Input from the basement and LAN4 as output to the first floor.

But do I have to define all possible VLAN's on both ports (WAN/LAN4)?
The downside is, if I create a new VLAN on the router in the basement, I have to change the switch in the ground floor, even I would like to use the VLAN only in the first floor.

Or is it ok to use a mix of tagged/untagged?
So I only have to define the VLAN's the dump ap is using for itself and any other TCP packets ( some with VLAN x, some without VLAN) are going through the untagged VLAN port.


Mixing tagged and untagged together on the same interface has caused trouble in the past with some devices. However, if it works for you, go ahead.

You can use your routers as "managed switch plus dumb access point", it works perfectly fine for me. I have several VLANs defined on my main router, some have dedicated LAN ports, some don't, and all are trunked together on a specific LAN port, that connects to the WAN port of a secondary router. And that secondary router has SSIDs for some VLANs, and LAN ports for others.