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silimiero
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Joined: Sun Jan 31, 2021 3:32 am

PPPoe to Static MTU issue.

Thu Oct 14, 2021 3:43 pm

Hello guys,
I need help regarding MTU.
I've received a pppoe connection and distributed that using Static IP.
I'm actually confused what should be the MTU for static IP user. It's effecting games ping. Currently my bridge is on MTU 1500 and users too.
PPPoE has MTU 1480.
Thanks in advance.
 
tdw
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Joined: Sat May 05, 2018 11:55 am

Re: PPPoe to Static MTU issue.  [SOLVED]

Thu Oct 14, 2021 5:35 pm

Static or dynamic addressing is irrelevant to MTU settings. For IPoE connections the minimum MTU should be 1500. For a PPPoE connection the maximum MTU is 1492 unless your ISP supports baby jumbo frames per RFC4638.

With a mix of connections supporting differing MTU sizes you either end up with packet fragmentation or larger packets being dropped if fragmentation is not permitted. Path MTU discovery https://en.wikipedia.org/wiki/Path_MTU_Discovery should resolve this, but misconfigured/broken implementations can prevent this operating correctly. MSS clamping is often employed as a workaround - this reduces the suggested segment size during a TCP handshake to ensure the packets will not be fragmented.

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