On 2017-04-09, Pierre Emeriaud <[email protected]> wrote: > 2017-04-09 16:33 GMT+02:00 Edgar Pettijohn <[email protected]>: >> On 04/09/17 04:45, Florian Ermisch wrote: >>> >>> Hi Edgar, >>> >>> check the MTU on your tunnel device. >>> You can give it a try with >>> doas ifconfig gif0 MTU 1400 > > >> Unfortunantly that didn't do it. I think I'll just wait until my ISP offers >> it. I'm guessing my problem is the gif0 tunnel. Hopefully one day without >> the tunnel it will work. > > Check on tunnelbroker.net in the tunnel details, in the "Advanced" tab > you can set the tunnel mtu. > > With a mtu of 1500 on the physical interface, the maximum mtu possible > is 1480. It's the defaults at he.net iirc, but that doesn't hurt to > check it's not at 1280 (minimum allowed ipv6 mtu). > >
Yes, that needs checking. Also if things are OK from the router but not from a machine behind it, you may need to either use "scrub max-mss" to restrict MSS in TCP SYNs to artificially reduce the MTU (at least for TCP...won't help UDP or less common protocols...) or configure a lower MTU on the internal interface (on both sides: router and all clients).
