Also, this may be a nuance of this type of hardware, but this looks fishy to me. Compared to what's in robocfg show, I would expect only vlan2 to contain eth0 since vlan1 is supposed to contain the local radios/br0, right?
mreckhof@RT-AC56R-CE50:/proc/7210/net/vlan# cat /proc/net/vlan/config...