I have been searching the internet for a few days now for a solution to this problem and I have found no solution yet.
I just installed Ubuntu 14.04.3 on a server and my server sporadically and selectively stops responding to pings, drops all connected sessions and stop accepting web server requests. I say selectively because I send pings from different machines and server responds to some and does not respond to the others at the same time. I believe it must be a security setting or firewall setting but I have not been able to find any solution to this issue. Please someone help me. Thanks