You are here

How to set the MTU size on an external interface

OLD: Affects version(s): 

For certain network infrastructures it is necessary to set a specific MTU size different from the 1440 bytes set by a regular Airlock.

To set specific MTU sizes for back-end or management interfaces, follow the instructions in the article "How to set the MTU size on  back-end or management interfaces".

Follow these steps to alter the MTU size for all external interfaces:

Airlock 5.0

1. Log in with user "root"
2. # vi /opt/airlock/netcfg/conf/
3. Change the front-end default MTU_EXT_IF="1440" to the needed value

PHYS_IF_EXT_WWW="${configHelper.stringListToString(${networkHelper.physicalExtIfNames}, " ")}"


4. Save the file with :wq!
5. Activate your current configuration
6. Restart the netcfg service (# service airlock-netcfg restart)
7. Verify your new setting (# ip link show)

Airlock 4.2.x

  1. Log in using SSH with user "root"
    # vi /opt/slt/ses/netcfg/
  2. Change the setting MTU_EXT_IF="${staticValues.MTU_EXT_IF}" to e.g. MTU_EXT_IF="1430"
  3. Save the file with :wq!
  4. Load the template file with
    # svcadm restart svc:/site/slt_alec_agent:default
  5. Activate this configuration in the Configuration Center by clicking on the "Activate" button
  6. Set the values to the interface with the network configurator
    # echo "RE_CFG_EXT_PATH" > /tmp/root/netcfg.mode
    # svcadm refresh svc:/site/slt_netcfg_extern:default

With the command ifconfig -a you will see the currently active value for MTU.

The altered MTU_EXT_IF value will remain active after configuration changes or reboots. However, your changes may be lost when installing an official  Airlock update. Please check your configuration after each update.

Knowledge Base Categories: