PTR Record

I have an ongoing problem with an SBS2003 Server. Everything seems to work during the day but I have an issue that at artound 18.30 each day users lose connection to the Server.

However, they do not lose Network connectivity as I can ping the Servers and the Internet works. It is Outlook (running on the Exchange Server) and a shared database that show the problem.

Outlook freezes and if you wait long enough and close it when reopened it prompts for the user name and password. As regards the database the drive mapping is lost which results in the database failing.

If you enter the user name and password into Outlook the drive letters are reconnected and everything will work fine.

During the problem I have had a PC running a ping permanently to the Server and this did not break. I also had a PC downloading a 4Gb file during this time and that worked fine.

SOmeone has suggested a DNS problem and that I run "nslookup ip"

When I do this I get the error: sbserver2003.domainname.local can't find: Non-existent domain.

I believe this is a PTR rpblem. However, when I look at the DNS server and the reverse lookup the server is listed and looks fine.

I have also rerun the Internet Connection Wizard and changed the External IP to a new one to see if that helped.

I am getting desperate as this has been going on for a long time and I have posted different questions here to try and reslove it but nothing is working.

No restrictions are set for user logons and they have the problem whether the are in OUtlook or the Database.

Optima SystemsNetwork EngineerAsked:
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Have you checked, if there are any scheduled tasks for this time (DB-cleanup, backup, ...)? Is the DNS-server replicating to a second one? Are there any scheduled tasks on the clients for this time?
Miguel Angel Perez MuñozCommented:
Maybe you have two different problems.

Search on server program task starting at 18:30, maybe a av scan or whatever are disrupting to users.
Reverse DNS resolution not affect to normal client connection, because when clients startup, must to resolve and a DNS problem must be appear on this stage, and usually DNS resolution is not reverse, usually name must to resolve to an IP not backwards.
Have you create your reverse DNS zone on your internal DNS server?
Optima SystemsNetwork EngineerAuthor Commented:
there are no scheduled tasks set to run at this time.on either the Server or PCs.

I do not understand about the DNS question. It was suggested it could be a DNS issue and the error I am getting concerns me. However, the problem does not arise during the day.
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Do you get this nslookup error only at about 18:30 or at any time of day?
Optima SystemsNetwork EngineerAuthor Commented:
at anytime during the day.
In this case I would check my DNS-setup. Nevertheless, I don't really think this would solve your general problem. As the problem arises periodically at a given time, it really looks to me, as if there is some kind of scheduled task on any device in your network that seems to interfere with your other systems. You will have to check all devices for scheduled tasks, including routers, switches, firewalls and all servers and clients. If it was a general problem with DNS only, you would experience the problem through the whole day.
Another possibility could be, that you have a client (maybe a roadwarrior), that is shutdown at about 18:30. This client could have some awkward configuration that leads to the problems when it is taken off the network. I had something similar in a company, where every now and then the whole network went down to 10MBit and some time later it recovered again to GBit-speed. The problem was a notebook of an employee that came now and then into the company and plugged his notebook in. His notebook was configured with 10MBit and the switches dropped all ports to 10MBit as long as he was connected. We found this out after over 6 month of debugging all kind of hard- and software.
Optima SystemsNetwork EngineerAuthor Commented:
Thanks, I will go back through the Server / switches etc....

The odd thing is that it happens to some but not all PCs. Also those that are robooted come back on but then a few minutes later some others will drop off.

I have changed some PCs to MS Security Essentials rather than McAFee.

Do you know an easy way to check that there is no Group Policy which has someohw become enabled which logs users off but allows them to reconnect again.

My real problem is that it is not always the same PCs. They do not go off at the same time although it is always between the hours of 18.00 and 19.00.

The Server does not need rebooting to make it all work in the morning.

I have had this issue since Christmas. We added a spare router to split the internet but that was switched off and the problem still happened.

Backups do not run until 23.00.

Maybe it is Exchange doing a defrag but if this were the case surely thay would not be able to log straight back oin?

Do you know where i can check when the Exchange maintenance runs.
Optima SystemsNetwork EngineerAuthor Commented:
I fixed all the IPS on the PCs and the problem went away. Still no understanding why it happened

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Optima SystemsNetwork EngineerAuthor Commented:
In the end it must have been that there were 2 routers on the network and although both had DHCP disabled and there were no problems in the day something hapened at 6 o'clock to knock the PCs off the network. By fixing the IPs for each PC the problem has not arisen again.
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