vlan40

 /int bridge add name=br-wan vlan-filtering=yes auto-mac=no admin-mac=[/int ethernet get [find default-name=ether1] mac-address ]

 /int bridge port remove [find interface=eth1-gateway]
 /int bridge port remove [find interface=eth5]

 /int bridge port add bridge=br-wan interface=ether1
 /int bridge port add bridge=br-wan interface=ether5 pvid=40

 /int bridge vlan add bridge=br-wan vlan-ids=40 tagged=ether1

 /interface vlan remove [find vlan-id=40]