In the past week, my office has switched from IDSL to Cable service. In doing so we had to purchase a new router for the system. We are running off of a Windows 2000 server with mostly XP Professional PCs. Everything is working just fine, except for the fact that overnight, all of our computers lose their network connections, but still have internet access. The problem is solved by logging out and logging back in. This is a minor irritation for most, but we do have some machines that need to stay on the network constantly for data acquisition. We did not have this problem prior to switching service providers. I have tried two different routers (the first one was a belkin and I have not heard rave reviews--now working with a D-Link) but to no avail. I have looked at everything that I can think of on the server and the PC's to make sure that they were not being logged off automatically, everything looks fine. Does anyone have any idea what could be done to fix this problem?

Have you asked your new ISP about this problem?

yes, I've talked to them. They said that it is a network issue, probably the router. I called the technology company that setup our network initially and no one there really knows what to do either.

Might start by posting your network topology. Router is just a gateway and should have no effect on internal network connectivity. That would be a switch or server issue. Are you forwarding in DNS to the isps DNS? If not this could be a problem with authenicatiion. What do the server event logs say? Managed switch? What does its logs say?

When you are experiencing the problem, can you ping the server? If yes the problem is probably with the server. Probably a process (backups?) that is disabling the users session. This does not sound like a router issue. Especially as you said you have tried two different routers which would have two different configs. Here is one common router problem: Some routers can set to not allow network access during certain hours like at night. When people come back in the morning the router now allows access. Their session with the server timed out though during the night when the router hit those hours. I would also check the security event log on the server. See if anything that might even remotely be applicable. As a short term fix and way to dignose the issue you could set up a ethernet concentrator (or switch), connect the PC's to it and then one port to the router. If you have the same problem the next morning you have just established definitivly whether it is th server or router.

I could ping the server from my pc this morning when I could not access the network. I don't really have a background in IT, I'm a chemist who has started wearing more and more "hats" around the company because I've got some free time. I've developed the company's website and have been able to take care of most of the issues that have come up with the computers so far, but I am far from being "knowledgable", so keep that in mind. As for "network topology" I have gathered (from google) that you probably mean the setup of the different components. In that case, we've got a cable modem connected to a router, connected to a switch, connected to our server. As to the question about "forwarding in DNS to the isps DNS"--I don't know. Can you give me some more info about how to check that? The router is not set up to limit access between certain hours. I went and looked at the server logs and found this: System log: lots of errors from the past few days. Source: netlogon--registration of the DNS record failed with the following error: DNS operation refused. Security log: empty Application log: just information messages DNS Server: last message was from 2 days ago Error-DNS server has updated its own host(A) records...an attempt was made to update them with the new records through dynamic update. An error occurred during this update. If this is a problem with a process disabling user sessions, why did the problem just start with the change from dsl to cable? wouldn't it have been there before? Thanks for all of the help, everyone. This is the only place that anyone has been able to give me helpful information--I finally feel like progress is being made. I really appreciate it.

If you have a seperate (not integrated) switch from the router then the 'network' (server, desktops, switch) should not have been even touched when you changed from IDSL to cable. Please tell us whetyher the desktops are connected to the switch or the router. Yes it would make it appear then the network should not have the problem. There is only one problem that could result from the Internet/router side which is too many packets going to the server (Denial of Service attack) which could cause your problems. Would think that is a remote possibly but could happn. But when looking at the network side and the poblem you have it does sound like a server issue. It just may be a coinsidence it hppend the same time as changing internet access. You mention the system log having lots of errors. That means you need to fix the problems. One of which may be causing this main problem. Be nice to now some of them if they're not a trade secret....Also why do you not have any entries in your security log? That is not good.