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We have a simple office network with the following structure: DSL Modem -> Checkpoint 620 -> TP-LINK TL-SG1016 -> Ethernet ports around the office -> Computers & Printers. The CP620 also have Wi-Fi on with a password for some mobile devices.

  1. All of the devices are getting their ip`s & DNS from the CP620, based on their MAC Address.

  2. All computers are running Windows 8.1 + Bitdefender GravityZone endpoints with the same policy.

  3. All devices are working perfectly.

There is one computer which loses it`s internet connection (but not the local network connection) every few hours, for 10-20 minutes. It has the exact same hardware like the rest of the computers. It has the Same updates and drivers installed. A restart sometimes help.

I have tried:

  1. Changing DNS addresses to OpenDNS, GoogleDNS and manually inputting the ISPs DNS in the computers network settings.
  2. Skipping the patch panel, old cables and old Ethernet port, and connecting the Computer directly to the Switch.
  3. Reinstalling Windows.
  4. Resetting BIOS
  5. Comparing The computer`s settings to the other computers.
  6. Resetting and re-configuring the router and modem.
  7. Installing different NIC driver`s (older version).
  8. Disabling VirtualBox virtual network interface.
  9. Trying linux, which as far as I remember, showed the same behavior.
  10. Installing a PCI-E NIC, and using it instead of the built-in motherboard NIC.

None of these helped.

The network is very simple. No special polices, proxys, everything that is blocked or allowed on one computer, is blocked and allowed on the rest of the computers. The strange part is that that previous computer that was in this physical area, showed the same behavior. It had totally different hardware, ran Windows XP, and was connected to an older switch at that time.

While I am not system admin, I am the guy currently taking care of the computers and network, and I find this specific issue a very strange one. I would appreciate your help, and will provide any log/info/tests results necessary.

Thank you very much, Noam.

EagleX
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  • You've given us a lot of information but you haven't actually told us the exact symptoms of the problem. **There is one computer which loses it`s internet connection** could mean absolutely anything. What are the actual symptoms of the problem? Can't resolve DNS names? Can't ping external ip addresses? What? – joeqwerty Jan 11 '17 at 16:43
  • Hey Joe, thank you for your response. Cant resolve DNS names (for example: " Warning 08/12/2016 13:45:27 Microsoft-Windows-DNS-Client 1014 (1014) Name resolution for the name 2015.uploaded.fresh.co.il timed out after none of the configured DNS servers responded.), and as far as I remember, I`m 99% sure it also cant ping external IP addresses. I will check that again on Sunday, but as for now, it`s yes to both questions. – EagleX Jan 12 '17 at 17:53

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