IPv6 and PPPoE with MSSFIX

Daniel Gröber dxld at darkboxed.org
Wed Aug 23 17:14:51 UTC 2023


On Wed, Aug 23, 2023 at 04:58:40PM +0200, Marek Küthe wrote:
> PPPoE adds 8 bytes of overhead so that an MTU of 1432 can be used. I
> also have to do this at home with my DSL line for example.
> The MTU should be set on each side (on both peers) for this to work.

Oh, I just realized I used the 1432 MTU in my earlier reply based on
Marek's math but since Luiz's underlay network is IPv6 this is not actually
correct. MTU=1440 is only correct on top of IPv4, for IPv6 the "optimal"
MTU is 1420 so with PPPoE involved that's MTU=1412.

  1500 Ethernet payload
   -40 IPv6 header
    -8 UDP header
   -32 Wg header
    -8 PPPoE
  1412 wg tunnel MTU


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