# ifconfig {vlan-name} create

To associate the VLAN interface with a physical interface and assign a VLAN ID, IP address, and netmask:
# ifconfig {vlan-name} {ip-address} netmask {subnet-mask} vlan {vlan-id} vlandev {physical-interface}

The following examples, all packets will be marked on egress with 802.1Q VLAN tags, specifying a VLAN ID of 5:
# ifconfig vlan5 10.0.0.1 netmask 255.255.255.0 vlan 5 vlandev em0

To remove a VLAN interface, enter:
# ifconfig {vlan-name} destroy