Copyright (c) 2000 The NetBSD Foundation, Inc.
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by Jason R. Thorpe of Zembu Labs, Inc.
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.Dd June 26, 2001 .Dt VLAN 4 .Os .Sh NAME .Nm vlan .Nd IEEE 802.1Q Virtual LAN network device .Sh SYNOPSIS .Cd "pseudo-device vlan" .Sh DESCRIPTION The .Nm interface provides support for IEEE 802.1Q Virtual LANs. This allows the trunking of more than one network on a single network interface. This is particularly useful on routers or on hosts which must be connected to many different networks.
p To use a .Nm vlan interface, the administrator must first create the interface and then specify the VLAN tag and physical interface associated with the VLAN. This can be done by using the .Xr ifconfig 8 .Sq create , .Sq vlan , and .Sq vlanif subcommands, or .Dv SIOCSIFCREATE and .Dv SIOCSIFVLAN ioctls.
p To be compatible with others 802.1Q devices, the .Nm interface shall support a 1500 bytes MTU, which means that the parent interface will have to handle frames that are 4 bytes larger than the ethernet MTU. Drivers supporting this increased MTU are: l -dash -compact indent t drivers using the dp8390 core .Ns ( Ns Xr ec 4 , .Xr ne 4 , .Xr we 4 , possibly others) t .Xr ea 4 t .Xr eb 4 t .Xr epic 4 t .Xr ex 4 t .Xr fxp 4 t .Xr le 4 t .Xr tlp 4 t .Xr ti 4 t .Xr xi 4 .El .Nm can be used with devices not supporting the 802.1Q MTU, but then the MTU of the .Nm interface will be 4 bytes too small and will not interoperate properly with other 802.1Q devices, unless the MTU of the remote end is also lowered. .Sh SEE ALSO .Xr ifconfig 8 .Sh HISTORY The .Nm device first appeared in .Nx 1.5.1 . .Sh BUGS The .Nm interfaces do not currently inherit changes made to the physical interfaces's MTU. .Sh AUTHOR The .Nm driver was integrated by .An Andrew Doran .Aq ad@netbsd.org and .An Jason R. Thorpe .Aq thorpej@zembu.com . It was derived from a VLAN implementation that appeared in .Fx and .Ox .