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Firewall Blocks Access From Other LAN Computers Intermittently
I have Norton Security, and for the last few years, I have had problems with intermittent blocking of computers on the LAN to one another. I have spent more hours than I can count trying to track down this problem. Some times computer 1 could see computer 2, but not the reverse. Sometimes it would switch. Sometimes in the morning they could see each other, but in the afternoon they could not. Sometimes one computer could not see another for weeks at a time. Sometimes a computer would be blocked for just a few minutes. The periods when one computer could not see another was intermittent; it was all over the map.
When a computer was blocked, it could not ping the other, by name or by ip address. No file sharing could occur during blocked periods. But all the computers had unfettered internet access. For years, I thought that it was a dns problem, or something with the server, because it was periodically happening to all the computers in the company. I have changed servers, routers, switches, everything, to try and track down this problem.
I finally tracked it down to Norton Security. When I turn off the firewall, everything clears up. I can turn the problem on and off by toggling the firewall on and off. I tried resetting the firewall in the Norton Settings section on each computer and that had no effect. Only completely turning off the firewall would solve the problem.
It's not caused by old Norton installations, because it would happen to brand new computers that only had the latest Norton Security installed. The most recent computer is a Windows 10 workstation that we just put together last month. We don't use Windows Firewall, so that should not be interfering with Norton.
Does anybody have a solution to this problem?