mtu on Linux vs MacOS

[Harald Dunkel]

Hi folks,

I am using PPPoE to connect to my IP provider. To use wireguard on Linux I
have to reduce the MTU in wg0.conf to 1400. Using the default 1420 a ssh
connection tunneled through wireguard gets stuck (reproducible). An echo
of a very long line (e.g. 4096 chars) is sufficient.

The weird part is, MTU 1420 works fine for wireguard on MacOS. How comes
that Wireguard appears to be more stable on MacOS than on Linux?

Peer is OpenBSD 6.8.


Regards
Harri