Setup:
* WiFi device `wlan0` up and running as AP as slave to bridge `br0`.
Bug:
* Adding a vif (VLAN interface) to `br0` fails.
```
vyos@apu2# set interfaces bridge br0 vif 100 address 10.66.66.254/24
[edit]
vyos@apu2# compare
[interfaces bridge br0]
+ vif 100 {
+ address "10.66.66.254/24"
+ }
[edit]
vyos@apu2# commit
You must first activate "enable-vlan" of br0 bridge to use "vif"
[[interfaces bridge br0]] failed
Commit failed
[edit]
vyos@apu2# discard
Changes have been discarded
[edit]
vyos@apu2# set interfaces bridge br0 enable-vlan
[edit]
vyos@apu2# compare
[interfaces bridge br0]
+ enable-vlan
[edit]
vyos@apu2# commit
Can not add interface "wlan0" to bridge, VLAN aware cannot be set!
[[interfaces bridge br0]] failed
Commit failed
[edit]
vyos@apu2#
```
Maybe the quirks below might be linked to this issue:
When configuring WiFi interfaces as bridge slave interfaces, they must be configured to accept a specific address mode. This is explained in https://w1.fi/cgit/hostap/plain/hostapd/hostapd.conf .
```
# For nl80211, this parameter can be used to request the AP interface to be
# added to the bridge automatically (brctl may refuse to do this before hostapd
# has been started to change the interface mode). If needed, the bridge
# interface is also created.
#bridge=br0
# WDS (4-address frame) mode with per-station virtual interfaces
# (only supported with driver=nl80211)
# This mode allows associated stations to use 4-address frames to allow layer 2
# bridging to be used.
#wds_sta=1
```
This had already occurred in the past and been resolved in https://vyos.dev/T2210.