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I am having a issue with the domain at work (P.S I am not an IT prof.) and I was hoping someone could help me debug what is happening or point me in the direction of where to look.

The whole thing comes down to the fact that some of the Computers seem to be "dropping" off the domain. But its strange because I can still log in as domain\UserName from the computer, but when I look at the Networking And Sharing Center it doesn't show the domain, it just sees a network, and programs that use to run fine suddenly get timeout errors. As well it has been happening in such a way that first one computer drops off the domain then another and so on. If however I log on to one of the Computer that is still "on" the domain it works fine. But slowly all the computers are dropping off.

I have been doing a bit of looking around, but I'm still confused as to what's going on. These are some relevant points:

  1. All the computer that have dropped off, under windows firewall it says the domain is not connected, firewall is on
  2. All the those computers except for 1 I cannot ping from the server but I can ping the server from them.
  3. I also cannot ping between any of the PCs that are off domain.
  4. Note all these computers used to work fine on the domain, nothing has changed (except a new router was put in but none of the computers are connected through the router, they all go through a switch).
  5. It also seems to only affect the computers and not the users. I can log on to another computer and use everything fine.
  6. Under the System section the domain is set.
  7. I can still log on to those computers, even after setting the cached logon to 0.
  8. The server is Windows SBS 2003 and all the computers run Windows 7.

I am not sure if I have supplied enough information, but if someone could point in the direction to possibly narrow down what might be the cause or any help at all would be greatly appreciated.

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3  
DNS. It's always DNS :-) Seriously though, check your clients are using a Domain Controller as their DNS Server. Also check that the new router isn't issuing DHCP addresses. –  Ben Pilbrow Jan 22 '12 at 23:09
    
@BenPilbrow O.o apparantly the DHCP on the router was on so i switch it off. But when I did that and restarted the computer I got "No Logon Servers Available ... so on", however I am assuming the DHCP server on the computers are playing a role because this "dropping" has only occured on pcs that have been restarted O.o so could that mean that it simply is DC is not being used as the DNS as Robin pointed out? –  Heinrich Jan 22 '12 at 23:58
    
I updated my answer now you've discovered this. –  Ben Pilbrow Jan 23 '12 at 0:26

4 Answers 4

up vote 5 down vote accepted

I would immediately suspect the new network hardware that went in is issuing DHCP addresses, which the affected computers are using. I would also suspect this new hardware is setting itself as the DNS server, which will be the root of your issues.

Edit: Now you've discovered this is the problem, you have a couple of options:

  • If your Domain Controller is hosting the DHCP service, simply turn off the DHCP server on the router. Next time the computers send a DHCP request, the Domain Controller will respond accordingly.
  • If your Domain Controller is not hosting DHCP, I would recommend installing the built in DHCP server because this very tightly integrates with Active Directory and DNS. If installing DHCP is not an option, you will need to turn DHCP back on in the router configuration and change the DNS servers to point at your Domain Controllers.

If you start to have problems, fire up Wireshark and see what DHCP activity (or lack of) is happening on the network.

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Thanks For the Help :D I believe I have sorted it, I have gotten it working :D turns out the person who installed the router (wasn't me :P) left the DHCP server on, as you stated, so i turned that on and manually set the clients DNS servers to the DC, and its all seems to be working :D Again Thanks For the Help :D –  Heinrich Jan 23 '12 at 0:41

Are the client PC's using a DC for DNS?

Try running dcdiag to see if it comes up with anything. http://activedirectorytools.net/dcdiag-domain-controller-diagnostic-tool

Also remove a client from the domain and rejoin it and see if there is anything of interest in %windir%\debug\netsetup.log

Also when the clients were set up - did you use the OEM windows build, install windows one by one, or did you image them? If you imaged them you must run sysprep or newsid (I wouldn't recommend newsid though as this method is unsupported). Client's with duplicate SID's will eventually have issues (sometimes intermittent).

Edit - the other replies have also probably hit the nail on the head with the router running DHCP and only giving it's own address for DNS. Also it is likely not giving the correct domain name - can check for this by running ipconfig /all on an affected client, and ensuring it has the correct DNS server(s) and domain name.

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Yup, I suspect something funky is going on with DNS as well. –  Ben Pilbrow Jan 22 '12 at 23:18

Sounds like a time sync issue. Make sure that the DC has a reliable time source and that the workstations sync their time with the DC.

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Definitely check the Router. I've just installed a new device that has an onboard enabled DHCP so it can issue Ip addresses to VPN clients. It appears that when pc's attempt to renew an ip address, it goes here in preference to the DHCP on the DC.

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