vlan(4) - NetBSD Manual Pages

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VLAN(4)                   NetBSD Programmer's Manual                   VLAN(4)

vlan - IEEE 802.1Q Virtual LAN network device
pseudo-device vlan
The vlan interface provides support for IEEE 802.1Q Virtual LANs. This allows the trunking of more than one network on a single network inter- face. This is particularly useful on routers or on hosts which must be connected to many different networks. To use a vlan interface, the administrator must first create the inter- face and then specify the VLAN tag and physical interface associated with the VLAN. This can be done by using the ifconfig(8) `create', `vlan', and `vlanif' subcommands, or SIOCSIFCREATE and SIOCSIFVLAN ioctls. To be compatible with others 802.1Q devices, the vlan 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: - drivers using the dp8390 core ( ec(4), we(4), ne(4), possibly others) - ex(4) - fxp(4) - le(4) - tlp(4) - epic(4) - ti(4) vlan can be used with devices not supporting the 802.1Q MTU, but then the MTU of the vlan interface will be 4 bytes too small and will not interop- erate properly with other 802.1Q devices, unless the MTU of the remote end is also lowered.
The vlan device first appeared in NetBSD 1.5.1.
The vlan interfaces do not currently inherit changes made to the physical interfaces's MTU.
The vlan driver was integrated by Andrew Doran <ad@netbsd.org> and Jason R. Thorpe <thorpej@zembu.com>. It was derived from a VLAN implementation that appeared in FreeBSD and NetBSD 1.5.1 September 27, 2000 1
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