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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...

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How is it connecting to the internet - via some kind of router on the LAN or some other method? –  SimonJ Nov 25 '09 at 19:50
    
It connects through an AT&T U-verse gateway. –  johnnyb10 Nov 25 '09 at 19:53
    
Are other computers that use the same gateway afected by this problem as well? –  Richard West Nov 25 '09 at 21:01
    
No, it's just the server. Thanks. One thing that just occurred to me is that the gateway is acting as a DHCP server, but so is the server that we're having problems with. Apparently, we need it to do that because we need it to give out WINS addresses, otherwise Outlook/Exchange doesn't work right, and the AT&T gateway doesn't give out WINS addresses. Could the fact that there are two DHCP servers on the network be causing this problem? And if so, how do we handle it? (Apologies if this is not well explained, my business partner is the one who knows more about this stuff but he is out today.) –  johnnyb10 Nov 25 '09 at 21:26
    
Have any cron jobs or scheduled tasks that happen on the hour? –  Citizen Nov 25 '09 at 23:21
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2 Answers

up vote 1 down vote accepted

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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Yes, getting the IP from the AT&T device, but the server itself is also acting as a DHCP server. (See above for why.) Apparently, the way this AT&T U-verse thing works, it has to assign an address to the server via DHCP; we can't just set it to a static IP. –  johnnyb10 Nov 25 '09 at 21:27
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Without looking at what the AT&T one can do, you should be able to disable the DHCP on it and have the Win server hand out all the IP's.

I actually do it the other way and have my router hand out the IP's, but I can specify the DNS to use with the DHCP so the DNS it has the workstations pointing to is the Win server. The Win server doesn't have a DHCP on it. I don't use WINS, don't have the DHCP server on the Windows server running and my exchange clients are fine. So you should be able to configure you network to work as well.

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