I have a GL-S1300 and had the same question as @JFlo. After mucking around all morning wondering why my vlan id=2 setting was not working for WAN, I found this thread.
I am using OpenWrt SNAPSHOT, r14966-7330348f2d (Linux 5.4.75), and for this version it's possible to reassign the internal vlan id used for the virtual wan interface. I changed it from 2 to 3 with sysctl:
# /etc/sysctl.conf
# Use vlan id=3 for virtual wan interface hack.
net.edma.default_group2_vlan_tag=3
net.edma.default_wan_tag=3
Then I set up my switch like this (port 0 is cpu and port 5 is wan):
# /etc/config/network
config switch
option name 'switch0'
option reset '1'
option enable_vlan '1'
# this vlan is used internally by the driver for lan
config switch_vlan
option device 'switch0'
option vlan '1'
option vid '1'
option ports '0t 1 2 3 4'
# this vlan is the one my isp requires for pppoe
config switch_vlan
option device 'switch0'
option vlan '2'
option vid '2'
option ports '0t 5t'
# this vlan is used internally by the driver for wan
config switch_vlan
option device 'switch0'
option vlan '3'
option vid '3'
option ports '0t 5'
I tested the vlan tag 2 with the current stable release 19.07.5.
Now it's possible to use vlan 2 together with the wan port, but the performance is only about 65% of the stock Asus firmware.
A "for me too" posting from me as I was directed here from my thread
The hardware is a D-Link DAP-2610 (got it wrong in the initial posting over there) and I would like to ask what I can try to make VLANs work with that hardware.
Thanks, will do.
In the meantime I made progress and got 3 VLANs working, I assume.
Right now I am waiting for the (remote) tester of the Wifis bridged to the interfaces.
I can't test that myself as I am a few hundred kms away from that hardware (yeah, that makes configuration extra fun).
In a few hours I should know more.
I will, though I wonder which commit did fix this, is it cdc8d4b46f08: ("ipq40xx: revert usage of VLAN S-TAG") or something else. It seems that on MR33, which has one port, tagging has chance to work because it behaves as if it were a "LAN" port, but for WAN this would not work as in #69.
Oh well, I wish but those patches left out a lot of devices in 02_network. I removed those devices since I have no way to test them. That's why I slowly add them to my custom build upon a requester willing to test them there.