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NetBSD 6.1.5 - man page for vlan (netbsd section 4)

VLAN(4) 			   BSD Kernel Interfaces Manual 			  VLAN(4)

     vlan -- IEEE 802.1Q Virtual LAN network device

     pseudo-device vlan

     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 net-
     works through a single physical interface.

     To use a vlan interface, the administrator must first create the interface and then specify
     the VID (VLAN identifier, the first 12 bits from 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 program, use the ioctl(2) system call with the SIOCSIFCREATE and
     SIOCSIFVLAN arguments.

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

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

     The following will create interface vlan0 with VID 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 inter-
     face.  All other hosts on the Ethernet connected to tlp0 which configure a VLAN and use VID
     six will see all traffic transmitted through vlan0.

     The same VLAN can be created at system startup time by placing the following in

	   vlan 6 vlanif tlp0


     The vlan device first appeared in NetBSD 1.5.1, and was derived from a VLAN implementation
     that appeared in FreeBSD and OpenBSD.

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

BSD					December 16, 2010				      BSD

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