Server loses Internet connectivity every hour on the hour

networkingrraswindows-server-2003windows-server-2008

I have a Server 2003 Small Business Server that loses Internet connectivity every hour on the hour, for about 15-20 minutes. I can't figure out what's causing it. The machine still has LAN connectivity, but it loses its Internet connection, and people who are trying to connect remotely (via RRAS) can't get in. Then, after about 15 min., it works again. I checked to see if any services are scheduled to run and are knocking it offline, but there doesn't seem to be anything. Checked Event Viewer and it looks normal. Any ideas as to what this might be? Thanks…

Best Answer

Regular intervals smells of DHCP problems. You're getting your IP from an external device, right? I'm no familiar with AT&T policies (different continent..) but sounds like your public IP address somewhat goes 'down'. I think the problem might not even be on your side..

[updated] 2 dhcp servers DO fight if they are on the same subnet. It works this way: at regular intervals your server sends out a message saying "hi, can I keep my IP?" and both servers answer. Apparently, after some struggle, your server gains its ip back.

Solution:

  • try limiting the scope of the gateway DHCP server to just one IP (using MAC addresses - but beware when you change network card)

or

  • (simple solution, might not be your case) use different network interfaces: one for the server-going-out, one for the lan

or

  • get a nat box/router between the gateway and the lan. Have the nat box grab the ip from the gateway. Do port mapping to tunnel connection through nat box to server.

Your mileage may vary but please do not put two dhcp on the same subnet! :)

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