MTU (PPoE) setting not working

[Darkling]

Hello,

I have a fiber connection from dutch provider KPN. I tried to setup my Asus AX88U via PPoE whit a MTU 1500 (rfc4638). i have Merlin 386.5 installed. After i change the value of MTU seize under PPoE settings, and did a test on my laptop

ping google.com –f –l 1492 i noticed that the MTU is still 1492, instead of 1500. Is this a known issue or did i something wrong?

I see allot of these in my logs:

Mar 14 20:54:11 start_wan_if(): Error setting MTU on eth0 to 1500
Mar 14 20:54:11 start_wan_if(): Error setting MTU on vlan6 to 1500

I did some tests. first one is MTU 1472 + 28= 1500
Pinging yahoo.com [74.6.231.20] with 1472 bytes of data:
Reply from 192.168.50.1: Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.

Ping statistics for 74.6.231.20:
Packets: Sent = 4, Received = 1, Lost = 3 (75% loss)

Looks that his one is correct. Here is the MTU 1492

Pinging yahoo.com [74.6.231.20] with 1464 bytes of data:
Reply from 74.6.231.20: bytes=1464 time=120ms TTL=48
Reply from 74.6.231.20: bytes=1464 time=121ms TTL=48
Reply from 74.6.231.20: bytes=1464 time=120ms TTL=48
Reply from 74.6.231.20: bytes=1464 time=121ms TTL=48

Ping statistics for 74.6.231.20:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss)

I also tried some older builds, but same results. The only way to get a MTU of 1500 is to put back the modem from my provider and setup the WAN type connection to automatic ip.

 

[Sxrtho]

The MTU in PPPoE is only 1492