Technical data

4. Packages

to work with VLANs should ensure that the respective Linux NIC drivers support VLANs

correctly.

OPT_VLAN_DEV Default: OPT_VLAN_DEV=’no’

’yes’ activates the VLAN package, ’no’ deactivates it.

VLAN_DEV_N Default: VLAN_DEV_N=”

Number of VLAN devices to conﬁgure.

VLAN_DEV_x_DEV Default: VLAN_DEV_x_DEV=”

Name of the device connected to a VLAN capable switch (iE ’eth0’, ’br1’, ’eth2’...).

VLAN_DEV_x_VID Default: VLAN_DEV_x_VID=”

The VLAN ID for which the appropriate VLAN device should be created. The name

of the VLAN device consists of the preﬁx ’ethX’ and the attached VLAN ID (without

leading ’0’). For example ’42’ creates a VLAN device ’eth0.42’ on the ﬂi4l-router.

VLAN devices on the ﬂi4l-router are always named ’ device . vid ’. So if you have an eth-

device connected to a VLAN-capable switch and you want to use VLANs 10, 11 and 23 on the

ﬂi4l-router you have to conﬁgure 3 VLAN devices with the eth-device as VLAN_DEV_x_DEV=’ethX’

and the respective VLAN ID in VLAN_DEV_x_VID=”. Example:

OPT_VLAN_DEV='yes'

VLAN_DEV_N='3'

VLAN_DEV_1_DEV='eth0'

VLAN_DEV_1_VID='10' # will create device: eth0.10

VLAN_DEV_2_DEV='eth0'

VLAN_DEV_2_VID='11' # will create device: eth0.11

VLAN_DEV_3_DEV='eth0'

VLAN_DEV_3_VID='23' # will create device: eth0.23

Please always remember to check the MTU of all units involved. Caused by the

VLAN header the frames will be 4 bytes longer. If necessary the MTU must be

changed to 1496 on the devices.

4.2.4. Device MTU - Adjusting MTU Values

In rare circumstances it may be necessary to adjust the MTU of a device. E.G. some not 100%

VLAN-compatible network cards need to adjust the MTU. Please remember that few network

cards are capable of processing Ethernet frames larger than the 1500 bytes!

DEV_MTU_N Default: DEV_MTU_N=”

This setting is optional and can also be completely omitted.

Number of devices to change their MTU settings.

DEV_MTU_x Default: DEV_MTU_x=”

This setting is optional and can also be completely omitted.

Name of the device to change its MTU followed by the MTU to be set. Both statements

have to be separated by a space. To set a MTU of ’1496’ for ’eth0’ enter the following: