PFC200 interface MTU setting persistence

I’ve ran into an instance where I need to adjust the MTU on a PFC200 interface, however I’m running into an issue with persistence.
I was given an initial procedure (thanks @tyrone.visser ), however it seems on FW22, the /etc/network/interfaces file is only used for the loopback.

# Network configuration is handled by netconfd.
# ifup/ifdown are only used for loopback device, currently.

auto lo

iface lo inet loopback

When the required line to adjust the size of the MTU is added:

post-up /sbin/ifconfig br0 mtu 1380 up

the MTU hasn’t changed after reboot. A query using ifconfig br0 shows an unchanged MTU.

Also, I’ve tried looking into this on another PFC200 with FW25, but even though FW25 is still using Linux distro PTXdist, it has no /etc/network/ folder at all.

Does anyone have any ideas?

Thanks goes out to Dirk Meihöfer who got me pointed in the right direction.

There is a different file to use to make it persistent.

Add the line:

/sbin/ifconfig br0 mtu 1380 up

to the file


Reboot the device and you’ll see an updated MTU.