VLAN(4) | Kernel Interfaces Manual | VLAN(4) |
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:
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.
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 VID six will see all traffic transmitted through vlan0.
The same VLAN can be created at system startup time by placing the following in /etc/ifconfig.vlan0:
create vlan 6 vlanif tlp0
December 16, 2010 | NetBSD 6.1 |