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How to set the MTU size on an external interface

OLD: Affects version(s): 
5.0
4.2.x

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/network-frontend-new.cfg.in
3. Change the front-end default MTU_EXT_IF="1440" to the needed value

...
PHYS_IF_EXT_WWW="${configHelper.stringListToString(${networkHelper.physicalExtIfNames}, " ")}"
MTU_EXT_IF="1300"
...

 

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/network_frontend_new.cfg.in
  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.

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