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How to set MTU size on back-end and management interfaces

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 on back-end and management network interfaces.

To set specific MTU sizes for external interfaces, follow the instructions in the article "How to set the MTU size on an external interface".

Follow these steps to alter the MTU size for back-end and/or management interfaces:

Airlock 5.0

1. Log in with user "root"
2. Set the management MTU_MGT_IF and/or back-end MTU_INT_IF size in this file (you will not find any default setting in this file for MTU_MGT_IF and MTU_INT_IF; you must create this new entry)
3. # vi /opt/airlock/netcfg/conf/network-backend-new.cfg.in

...
NETMASK_BACKEND_INT_VISIBLE="${networkHelper.getNetmask(${thisnode.ipInt}, ${netmasks})}"

# your MTU values are placed here:
MTU_MGT_IF="1200"
MTU_INT_IF="1250"
...

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

Airlock 4.2.x

1. Log in using SSH with user "root"
2. # vi /opt/slt/ses/netcfg/network_configurator.sh
3. Add values for MTU_MGT_IF and/or MTU_INT_IF after sourcing the config files:

...
# configuration for backend network
NEW_CFG_BACKEND="${CONFIG_DIR}/network_backend_new.cfg"
. ${NEW_CFG_BACKEND}

# your MTU values are placed here:
MTU_MGT_IF=1440
MTU_INT_IF=1440
...

4. Save the file with :wq!
5. reboot

After rebooting you will see the currently active values for MTU with the command ifconfig -a.

The altered MTU sizes 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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