Revisiting the weird MTU issue
Derrick Lyndon Pallas
derrick at pallas.us
Wed Apr 10 20:20:11 CEST 2019
MTU discovery isn't supported widely in my experience. My rule has been to set the interface to 1280, which is the minimum allowed.
~Derrick • iPhone
> On Apr 10, 2019, at 8:34 AM, Roman Mamedov <rm at romanrm.net> wrote:
> I use WireGuard over IPv6 on a PPPoE connection. The Internet interface MTU is
> 1492. By my calculations MTU 1412 on the WG interface should fit.
> However, the following occurs on various MTU combinations between the Remote
> (a server in a DC with full 1500 wire MTU) and Local WG interface MTUs:
> Fails or not, is whether a within-WG Remote->Local TCP connection (iperf3)
> works fine or hangs up after transferring a few initial bits of data.
> Remote Local Result
> 1420 1420 Fails (as expected)
> 1420 1412 Fails (weird)
> 1412 1412 Works (fair enough)
> 1420 1408 Works (super weird!!!)
> Now I hope I described the situation clearer than the last time posting about
> this, so maybe someone has an idea what could be the culprit?
> So far this doesn't cause too much issue, as I'm using on designated p2p links
> for when one of the peers is on this PPPoE, I just use 1412 on both sides. But
> still, surely the above shouldn't happen?
> With respect,
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