OPNsense Forum

Archive => 18.1 Legacy Series => Topic started by: jljb66 on July 11, 2018, 03:09:04 pm

Title: MTU calculation bug.
Post by: jljb66 on July 11, 2018, 03:09:04 pm

This is not a huge issue however when you setup a pppoe connection the default value of the MTU is 1500 and opnsense has a calculation value of 1492.

ie:
Calculated PPP MTU: 1492

The issue is that if you set the mtu to 1492 and click apply, the system comes back with a different calculated value of 1484. The value continues to go down as you choose the newer calculated value. I have set mine a 1492 and have ignored the calculated value. I don't believe this harms the WAN interface but I just thought I would mention it.

Title: Re: MTU calculation bug.
Post by: franco on July 11, 2018, 04:06:37 pm

The PPPoE header is 8 bytes long. If you keep decreasing the physical MTU the effective MTU keeps decreasing with it...


Cheers,
Franco