pppoe jumbo frames -RFC 4638

Started by keropiko, August 11, 2023, 08:09:51 AM

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Hello all

i have a pppoe connection that supports jumbo frames for 1500 MTU. I had inserted on my WAN interface the MTU to 1508 and in the INTERFACES overview, the MTU was correctly 1500.

I have noticed that after the latest update, although the MTU of the interface is set to 1508, the MTU in the interview section is 1492.

If i just press "SAVE" on the WAN interface, it sets again the MTU to 1500 of the pppoe, but if i reboot the firewall, it returns to 1492.

Same thing if i set the MTU to 1508 on the "point-to-point->devices->pppoe" section. At first the MTU is 1500 but after a reboot, it goes to 1492.

Thank you.


August 11, 2023, 05:42:32 PM #2 Last Edit: August 11, 2023, 05:53:08 PM by iMx
Can confirm I see the same.

Checking ifconfig output I see:

- Physical, 1512
- VLAN, 1500
- PPPoE, 1492

I don't see this. Although, I have no VLAN for my PPPoE Connection.

I have a dummy interface enabled (igb0 - Parent/Physical Interface) with an MTU of 1508 and no other settings, and the MTU of the WAN PPPOE Connection set to 1500 and it sticks even with a reboot (as it did before).

Something to do with VLAN in the new update?

Previously you didn't need to actually assign the VLAN interface - the post above suggests that a fix/work around is to now assign the VLAN interface, then re-set the 1508 MTU (1512 on the physical) there.  This didn't used to be needed.

Have done this, will reboot/test again the morning.