Why I kept losing network connection?

  • ljCharlie
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Post 3+ Months Ago

I kept losing network connection with my Windows 2003 domain controller server with DNS and DHCP installed. If I reboot the server computer then all my client computers can gain network and Internet access again. There is nothing major that's generated in the event log ethier. Somehow after a couple of hours all the network connection are lost again and I have to reboot the server computer again.

Any help is greatly appreciated! Many thanks in advance!

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  • whosonthedexs
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Post 3+ Months Ago

Does the clients DHCP service disable itself?
  • ljCharlie
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Oh! Thank you very much for trying to help me out. I am just about to give up on this problem.

No. I am almost 100% sure the DHCP client service is not disabling itself because all I have to do is restart the server computer and it works again. So I don't think it is the DHCP client service. I believed it has to do with either the DNS or DHCP on the server side, but I don't what exactly it is.

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Post 3+ Months Ago

Is your server listed as the first IP address in the order of the DNS being handed out to the client PC's. Other than that I would suggest taking a look at your switches also and see what they are doing when the server locks up. You could try and reboot the switches the next time that happens and see if that will unlock everthing for you. Let me know if you need anymore ideas. Also the help on win2003 is pretty good. Enjoy :D
  • ljCharlie
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Post 3+ Months Ago

Again, thanks for the effort.

Yes, my server is listed as the first with 192.168.0.2 then the rest is 192.168.0.10 and so on.

At first I thought it was the switch so I shut down the switch and restart it again but it's not unlocking all the connections. So at this moment, I'm pretty sure it's not the switch.

ljCharlie
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Make sure you don't have more than one DHCP server running. If you do, clients get their TCP/IP info from the first DHCP server they find. It may not be the one you want them to get it from. I assume you want it all to be handled by your Server's DHCP. I'm guessing that may be what's screwing up your clients, because they do go out and check periodically. My first thought would be make sure DHCP is turned off in any routers you are using and go from there. When we were playing with this at school last year, we had seven of us running our own Win2K server. As soon as we installed and tested it we always had to turn our DHCP servers off because it would wreak similar havok with the schools network.
  • ljCharlie
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Post 3+ Months Ago

I only have one DHCP server that's running and my client are getting their IP address correctly. I mean I can see their computer names listed in the DHCP server leases.

ljCharlie
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Post 3+ Months Ago

Are you using the defaults in the DHCP configuration?

What is the lease time set too?

In the mean time i shall do some investigation.

HAve you checked the event logs on the server??
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Post 3+ Months Ago

No, I configured the DHCP to to contain conver the ip addresses that I needed. I don't know what is a lease time. How do I find that out? Yes, I checked the event log hundreds of time and no error generated.

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Post 3+ Months Ago

On your DHCP server, right click your scope and go to properties. There you can change your lease time. It's the amount of time before a client's IP allocation is released. Once it is released, then the Client has to request a new one. This is done by a UDP broadcast. You can test this by increasing the lease time to a day or several days. I believe the default with Win2K server is 1 hour. That's a little low in my opinion, and what is happening is that your server is probably getting bombarded with requests to renew.
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Post 3+ Months Ago

Also to tag along if your renew time is one hour then the PC will start at the half way time of the lease to see if it can keep the same number or not. If it doesn't get a response to that request it waits till three quarters of the lease time has expired and do the same request. If the results are the same where it didn't get a response from the server it will let the lease run out and then do a broadcast looking for a DHCP server to assign it a new address. Enjoy :D


//also on a side note test out your cat5 connection from the server to the switch and make sure the cable is good. Also try and switch the server to another port on the hub, and see if that changes anything. Just a thought :D
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Post 3+ Months Ago

I think you guys are on the right track, and unfortunately I don't have
too many new ideas to add the discussion. I did want to point out
though, that the default lease time on a IP address is 8 days.

This is right out of win2k3 server's help files:
Quote:
When a scope is created, the default lease duration is set to eight days. In most cases, this value is sufficient. However, because lease renewal is an ongoing process that can affect the performance of DHCP clients and your network, it is sometimes useful to change the lease duration. Use the following guidelines to decide how to best modify lease duration settings for improving DHCP performance on your network:

If you have a large number of IP addresses available and configurations that rarely change on your network, increase the lease duration to reduce the frequency of lease renewal queries between clients and the DHCP server. This reduces some network traffic caused by clients renewing their leases.
If you have a limited number of IP addresses available and if client configurations change or clients move often on your network, reduce the lease duration to promote scavenging of old IP addresses by the DHCP server. This increases the rate at which addresses are returned to the available address pool for reassignment to new clients.

It may not be the exact answer to your question, but I would think it's
helpful in terms of understanding what might be happening. MD's & ATNO's
assessment might be the closest to what you need. Check the lease
times, and make sure it's not set to something ridiculously low (1hr) and
set it to a few days. i usually set my scopes to 6 days. It gives a nice
cycle to the workweek, and allows an IP to be retained pretty easily.

As I said, I'm not even sure that's what the problem is myself. I'm running
3 win2k3 servers with no problems like this, so I can only help think a bit. :?
  • ljCharlie
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Post 3+ Months Ago

Thank you everyone for all your suggestions.

UNFLUX, I think your right on the lease time. When I installed, I didn't change the default lease time at all. I did check all the Address Leases and the expiration date is this 11/28/03, so I'm guessing it's about 8 days.

One other thing, the server IP address is static and should not be listed in the Address Leases, correct? If this is true then that means the server ip address never gets renew, right? And if the server ip address never gets renew then why is the server losing all network connection as well and not just the client if it is a lease time issue. So I'm guessing it's not the lease time. Because once all the network connection have lost, even the server can not ping its own switch, the gateway ip address. If I double click on the Local Area Connection under Network and Dial-up Connection, it still listed as connected...but the server access anything of its own box.

And by the way, I'm not sure if this error in the event log has anything to do with it, but here's what I got in the event log daily even only 4 to 5 hours.

The error event log ID is 29.

Quote:
Source: W32Time
Type: Error
Description: The time provider NtpClient is configured to acquire time from one or more time sources, however none of the sources are currently accessible. No attempt to contact a source will be made for 14 minutes. NtpClient has no source of accurate time.

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.


As I said above, this error seems to generate every day if not 4-5 hours. I'm not sure if this is relating to the problem or not...but I did use this net time /setsntp:<sntp server ip address> to fix it. But it only lasted for a day or two...if I didn't reboot the server.

Anyway, again, thanks for all your time and effort.

ljCharlie[/quote]
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Post 3+ Months Ago

There is a scope of addresses that are assigned out to clients and then usually there is an exclusive range and in that exclusive range is your static IP's that don't get handed out. So that is where the server address would be, routers, network printers, and other stuff like that. Make sure that you also don't have the server address assigned to another device like a router or printer. That would cause mysterious problems with the network. Enjoy :D
  • ljCharlie
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I'm quite sure that the server IP address is not assigned to another device. However, I have not checked if those ip addresses are listed in the exclusive section. They should be listed in there, correct? Although I have not checked, I don't think I ever seen those ip addresses listed in that section.

ljCharlie
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Post 3+ Months Ago

example

192.168.1.1 thru 192.168.1.49 -------- exclusive range
192.168.1.50 thru 192.168.1.220 ----- DHCP range
192.168.1.221 thru 192.168.1.254 --- exclusive range

or

192.168.1.1 thru 192.168.1.49 -------- exclusive range
192.168.1.50 thru 192.168.1.254 ----- DHCP range

//either one would work and the first one would give you 82 static IP's and the second one would give you 49 static IP's with a larger DHCP range to be handed out to clients. Yes the server, routers, and I suggest network printers be in the exclusive range. In the above example you can play with the numbers for your network. Enjoy :D
  • ljCharlie
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Post 3+ Months Ago

If it's not in the exclusive but yet not in the Address leases, this still is not safe?

ljCharlie
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That I do not know, I always assign an exclusive and DHCP range that fills up a /28 that way I never run out of addresses to assign. Best guess is to put the server in the exclusive range and see if that solves your problem.
  • ljCharlie
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Post 3+ Months Ago

I'll take a look at that tonight.

ljCharlie
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:D let me know if that helped or hindered ;)
  • ljCharlie
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Post 3+ Months Ago

I'll let you know by tonight or tomorrow morning.

Many thanks for the help.

ljCharlie
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Post 3+ Months Ago

First off you guys are missing a few steps....

Number one, does the server remain connected to the internet. If not then you can rule out DHCP as the cause.

Number two, If you rule out DHCP then obviously it is something else. I think you were more on the track when you were thinking DNS. First step in any network troubleshooting is pinging clients, your server and your ISP's gateway and DNS server. Is your system a true DNS server or is it forwarding requests to your ISP's DNS Servers?

Best way to rule out a specific service is to restart the services individually. That will narrow it down a bit.

Good Luck.... :)
  • ljCharlie
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Post 3+ Months Ago

Thanks, simpleminded, for contributing to this problem. I am agreeing with you because once the network connection has lost, the server can not ping anywhere, clients, ISP DNS; another words, the server can not ping anywhere. I have not test if the server can even ping itself. And to answer your question, the my DNS is not a true DNS server. I do have it forward any unresolve address to my ISP DNS server.

ljCharlie
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you not having the IP address reserved could be the biggest part of the
problem as I see it. I think we all have the right idea, it's a matter of
putting it all together to find your solution ljCharlie.

the thing is, something like this is hard to work out because none of us
can sit there with you and help figure it out. It's a lot easier being able
to see it for yourself, because there may be something you aren't
pointing out that could what's really wrong. :?
  • ljCharlie
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Yes, I agree with you, UNFLUX. It is very hard trying to troubleshoot something that's not in front of you. And so far many of you in here have done an excellent job helping people out.

One more thought, let's say it's my server network card that's going bad. If it's going bad and kept losing connection, would this generate an event in the event log? And if the problem lies with the bad network card, would I still see under Local Area Connection Status as connected? Or would it generate some kind of error?

I have seen a couple of workstations that have bad network card and it would not ping anywhere. However, I have not checked if bad network card would generate some kind of error though.

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Post 3+ Months Ago

more than likely not an error, but rather a notification that the hardware
is not working properly. Then again, it may not generate anything for
you to see at all other than it's behavior. Just to rule it out, I would take
5 min and swap it out to see. Never know...
  • ljCharlie
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The problem is I don't have another extra NIC around. However, if it is a NIC failure, I would see it in the device manager, right?

ljCharlie
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Post 3+ Months Ago

UNFLUX wrote:
you not having the IP address reserved could be the biggest part of the
problem as I see it. I think we all have the right idea, it's a matter of
putting it all together to find your solution ljCharlie.

the thing is, something like this is hard to work out because none of us
can sit there with you and help figure it out. It's a lot easier being able
to see it for yourself, because there may be something you aren't
pointing out that could what's really wrong. :?


not necessarily... The best way that I have found to assure that your IP is reserved is to simply pick an IP for the server that is not in your scope. DHCP cannot assign anything this IP address because it not in the scope. That way it will be static and DHCP will have no authority over it. This is tried and true in my domain. I have almost 100% uptime for the last 2 months or so. I was having the same problem that you were having recently and found that RAS was the issue. I don't remember weither or not you said that you have RAS with NAT enabled. But I found that if I hit repair on that specific NIC in the network properties window. I would regain full operability again and then a few hours later it would go down. I ended up rebuilding the server and the problem is gone. Therefore I think that you are having a DNS resolution problem. Try this and see if it comes back up. Also try to restart each service indepently when you have this problem again and see which one makes it come back up. Good Luck :)
  • ljCharlie
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Post 3+ Months Ago

This is REALY weird because last night somehow my network server is still working after a long day runing. Anyway, I still don't trust it...I'll keep monitoring for another week or so.

By the way thanks, simpleminded. You are quite right on the DHCP not assigning anything ip that's not within its scope. I have run Windows 2000 Server and now 2003 server and I have not seen DHCP assigned any ip that's out of its scope.

However, to answer your question on RAS, I don'thave RAS setup on my server. But yes, I'll keep your suggestion regarding starting each service independently. The only problem with this is it will take a little longer to diagnose the problem since it takes about 4-5 hours to a day to notice that the network has lost all connections.

ljCharlie
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Post 3+ Months Ago

I am having a similar problem on my network. However to reestablish connection with the network/internet I ipconfig /release and /renew and all is well. The problem is that I have to do this 3 to 5 times a day. I have been fighting this problem for a while and can't seem to make any head way.

I realize that this is an old posting but if you resolved the problem.... what was it and how did you fix it?

Any help would be wonderful.

Thanks!
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