GRE tunnel stops working suddenly after a random amount of t

[problem_master]

I've tried with some simple GRE tunneling between servers using this guide http://wiki.buyvm.net/doku.php/gre_tunnel.

Both servers are running ubuntu server 12.04 LTS.

What happens is that it worked for about 16 hours when it suddenly stopped working. The servers won't ping eachothers GRE adresses. When I re-install either servers OS the gre tunnel works again for a random amount of time until it stops again. I've confirmed with NFO and the other server provider that it's nothing on their side/outside the OS.

I have no idea why it stops working and how to fix it or what to look for. I'm not super experienced with ubuntu/linux and have no idea where to start, I've tried googling for this but couldn't find anything relevant. Please help if you can!

[Edge100x]

Are you pushing a lot of traffic through the tunnel? If the system sees what it thinks is a DDoS attack, it might block it, as it has one check for traffic that does not match UDP/TCP/ICMP.

[problem_master]

Not a lot of traffic at all. Never more than 10 mbits. Where can I turn this feature off?

[Edge100x]

Please have your concern escalated to me through a support request so that I can check on it specifically.

The anti-DDoS feature is not something that you'd want turned off, so it would be a matter of tweaking it.