VLAN(4)

NAME
vlan, svlan - IEEE 802.1Q and 802.1ad pseudo-device

SYNOPSIS
pseudo-device vlan

DESCRIPTION
The vlan driver provides network interfaces supporting Virtual Local Area Networks (VLANs) on Ethernet networks. vlan interfaces implement virtual networks using the IEEE 802.1Q protocol. svlan interfaces implement virtual networks using the IEEE 802.1ad protocol.

svlan interfaces allow construction of IEEE 802.1ad-compliant provider bridges. vlan and svlan interfaces can be configured to provide QinQ or stacked VLANs.

The interfaces can be created at runtime using the ifconfig vlanN create command or by setting up a hostname.if(5) configuration file for netstart(8). The interface itself can be configured with ifconfig(8); see its manual page for more information.

vlan and svlan interfaces must be configured with a parent Ethernet interface to operate, and a virtual network identifier. Packets transmitted through a vlan or svlan interface will be encapsulated in their respective protocols and transmitted on the specified physical interface. 802.1Q and 802.1ad packets received on the parent interface will be matched to the vlan and svlan interfaces by their respective protocol and virtual network identifiers, and decapsulated for reception on the associated virtual interfaces.

The 802.1Q and 802.1ad protocols include a priority field. By default, the 802.1p priority in a transmitted packet is based on the priority of packets sent over the interface, which may be altered via pf.conf(5); see the prio option for more information. Alternatively, txprio can set a specific priority for transmitted packets.

vlan and svlan interfaces support the following ioctl(2)s:

SIOCSIFPARENT struct if_parent *
    Set the parent interface. The parent may only be configured while the virtual interface is administratively down.

SIOCGIFPARENT struct if_parent *
    Get the currently configured parent interface.

SIOCDIFPARENT struct ifreq *
    Delete the parent interface configuration. The parent may only be removed while the virtual interface is administratively down.

SIOCSVNETID struct ifreq *
    Set the virtual network identifier. Valid identifiers are in the range 1 to 4094.

SIOCGVNETID struct if_parent *
    Get the currently configured virtual network identifier.

SIOCDVNETID struct ifreq *
    Clear the current virtual network identifier. Virtual interfaces without a configured virtual network identifier will use 0 in their protocols tag field.

SIOCSIFLLADDR struct ifreq *
    Configure a custom MAC address on the virtual interface. When the virtual interface is using a custom MAC address the parent interface will be configured to promiscuously receive packets. When operating without a custom MAC address the virtual interface will inherit the parent interfaces MAC address. Configuring 00:00:00:00:00:00 as the MAC address will clear the custom MAC address configuration and resume operation with the parents MAC address.

vlan and svlan interfaces use the following capability on parent interfaces:

IFCAP_VLAN_MTU
    The parent interface can handle full sized frames, plus the size of the vlan tag.

vlan interfaces use the following capability on parent interfaces:

IFCAP_VLAN_HWTAGGING
    The parent interface will offload the encapsulation and decapsulation of 802.1Q frames.

EXAMPLES
Create an 802.1Q virtual interface on top of the physical interface em0, with virtual network identifier 5:

    # ifconfig vlan0 create
    # ifconfig vlan0 parent em0 vnetid 5
    # ifconfig vlan0 10.1.1.100/24

Create an 802.1Q VLAN interface on network 10, on top of an 802.1ad provider bridge on network 8, on top of the physical interface bge0:

    # ifconfig svlan0 create
    # ifconfig svlan0 parent bge0 vnetid 8
    # ifconfig svlan0 up
    # ifconfig vlan0 create
    # ifconfig vlan0 parent svlan0 vnetid 10
    # ifconfig vlan0 10.1.1.101/24

Configure an 802.1Q VLAN interface with a custom MAC address:

    # ifconfig vlan0 lladdr fe:e1:ba:d0:84:0e

Remove a custom MAC address from an 802.1Q VLAN interface:

    # ifconfig vlan0 lladdr 00:00:00:00:00:00

Force the use of priority 1 for transmitted packets, regardless of the packet priority:

    # ifconfig vlan0 txprio 1

SEE ALSO
inet(4), ip(4), netintro(4), hostname.if(5), pf.conf(5), ifconfig(8), netstart(8) IEEE 802.1Q standard, http://standards.ieee.org/getieee802/802.1.html. Provider Bridges, QinQ, IEEE 802.1ad standard.

AUTHORS
Originally Garrett Wollman <wollman@freebsd.org>.

CAVEATS
Some Ethernet chips will either discard or truncate Ethernet frames that are larger than 1514 bytes. This causes a problem as 802.1Q and 802.1ad tagged frames can be up to 1518 bytes. Most controller chips can be told not to discard large frames and/or to increase the allowed frame size.