I've been setting up my second tunnel recently and ran into a problem with connections to only some
Running Wireshark showed (black) TCP or SSL frames with info "[TCP Previous segment not captured]". "GET"s were not followed by "HTTP/1.1 200 OK"s. With secure connections, "Client Hello"s were not followed by "Server Hello"s. Failing HTTP connections showed "[TCP Previous segment not captured] [PSH, ACK]". Most failing HTTPS connections showed "[TCP Previous segment not captured] Continuation Data".
A little searching found posts on these forums that said:
1.) Problems with MTU could give sometimes-failing connections with these symptoms; and,
2.) (Bought me a clue) Using "ping -s packetsize" could test for MTU problems.
My pings started failing below the default MTU of 1480 (proto-41 MTU maximum) so I concluded I was on to something
I've used without problems a SixXS AYIYA tunnel with a default MTU of 1280 (proto-41 MTU minimum). So I decided to reduce my tunnelbroker MTU to 1280.
Voila! Worked like a charm
I'm sure I could adjust the MTU upwards but I'm happy and decided to leave it set to 1280.
For anyone having problems:
1.) Go to your Tunnel Details page on tunnelbroker.net and click on the "Advanced" tab;
2.) Use the MTU slider under Tunnel Options to reduce your MTU and then click "Update";
3.) Tear down and restart your tunnel from scratch;
4.) Test and see if your connection problems are resolved.