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I'm running Debian 7.4, KVM VPS with the latest updates. I'm getting UDP ports randomly closed for 2-10 minutes for no reason. I'm running gaming servers and the port tester shows the ports are closed. It restores to the normal state itself. All the gaming servers are unreachable at that moment, though TCP ports are fine: gaming TCP ports are responding, apache2 is functioning without any problem.

I've tried contacting the host and there are no issues on their side. iptables is completely empty; I tried both disabling it and adding rules to accept the connections to that ports. I'm not running any single firewall at the moment. I used to have fail2ban, I even used to blame it, but removing/stopping it didn't seem to help.

What could be the source of issue? Any suggestions on fixing the problem?

Traceroute says the following: http://er-mta.net/screenshots/cloud/Screenshot_at_2014_04_11__20_25_16.png

Gallardo994
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It could be the that the hosting provider is at fault. You can try traceroute -n -U -p portnumber hostname from a client machine to see how far the UDP packets get. While doing that, you can use tcpdump -pni eth0 "port portnumber" on both client and server to check if it may be the case, that the packets leave the client and never reach the server.

If the above shows that the packets leave the client without reaching the server, then any NAT or firewall on the path from the client to the server is a suspect. The traceroute output should narrow the suspects down.

kasperd
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