vlan(4) - NetBSD Manual Pages

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VLAN(4)                 NetBSD Kernel Interfaces Manual                VLAN(4)


NAME

     vlan -- IEEE 802.1Q Virtual LAN network device


SYNOPSIS

     pseudo-device vlan


DESCRIPTION

     The vlan interface provides support for IEEE 802.1Q Virtual Local Area
     Networks (VLAN).  This supports 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 through a single
     physical interface.

     To use a vlan interface, the administrator must first create the inter-
     face and then specify the VLAN tag (a 16-bit integer which distinguishes
     each VLAN from any others) and physical interface associated with the
     VLAN.  This can be done by using the ifconfig(8) create, vlan, and vlanif
     subcommands from a shell command line or script.  From within a C pro-
     gram, use the ioctl(2) system call with the SIOCSIFCREATE and SIOCSIFVLAN
     arguments.

     To be compatible with other IEEE 802.1Q devices, the vlan interface sup-
     ports a 1500 byte MTU, which means that the parent interface will have to
     handle packets that are 4 bytes larger than the original Ethernet stan-
     dard.  Drivers supporting this increased MTU are:

     -   drivers using the DP8390 core (such as ec(4), ne(4), we(4), and
         possibly others)
     -   bge(4)
     -   ea(4)
     -   eb(4)
     -   epic(4)
     -   ex(4)
     -   fxp(4)
     -   gem(4)
     -   hme(4)
     -   le(4)
     -   sip(4)
     -   ste(4)
     -   stge(4)
     -   ti(4)
     -   tl(4)
     -   tlp(4)
     -   wm(4)
     -   xi(4)

     vlan can be used with devices not supporting the IEEE 802.1Q MTU, but
     then the MTU of the vlan interface will be 4 bytes too small and will not
     interoperate properly with other IEEE 802.1Q devices, unless the MTU of
     the other hosts on the VLAN are also lowered to match.


EXAMPLES

     The following will create interface vlan0 with VLAN tag six, on the
     Ethernet interface tlp0:

           ifconfig vlan0 create
           ifconfig vlan0 vlan 6 vlanif tlp0

     After this set up, IP addresses (and/or other protocols) can be assigned
     to the vlan0 interface.  All other hosts on the Ethernet connected to
     tlp0 which configure a VLAN and use VLAN tag six will see all traffic
     transmitted through vlan0.

     The same VLAN can be created at system startup time by placing the fol-
     lowing in /etc/ifconfig.vlan0:

           create
           vlan 6 vlanif tlp0


SEE ALSO

     ifconfig(8)


HISTORY

     The vlan device first appeared in NetBSD 1.5.1.


AUTHORS

     The vlan driver was integrated by Andrew Doran <ad@NetBSD.org> and
     Jason R. Thorpe <thorpej@zembu.com>.  It was derived from a VLAN imple-
     mentation that appeared in FreeBSD and OpenBSD.


BUGS

     The vlan interfaces do not currently inherit changes made to the physical
     interfaces' MTU.

NetBSD 3.0.1                      May 6, 2003                     NetBSD 3.0.1