SBS 2003 - Clients Lose Connection @ approx 6:00 every day.

Posted on 2005-03-04
Medium Priority
Last Modified: 2008-07-31
I have recently put in a new dell server with SBS 2003.
For some unknown reason, Every workstation machine on my network will experience some form of connectivity or permissions loss every night at approx 6:00.

Workstations can sometimes still contact the server, but at an alarmingly slow rate, or sometimes not at all.
Any Ideas, why allways at the same time?

Question by:HarperBen
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LVL 10

Expert Comment

ID: 13463833
Check the event logs on the server and find out what's happening at that time. Make sure your switch is on a UPS and isn't losing power.

Author Comment

ID: 13463922
Its all on UPS.
Im going to clear all my logs.
I need to see what logs are occuring daily at the problematic time, But theres to much to wade through.
Ill leave it a few days and see whats happenig everyday @ 6:00
LVL 23

Expert Comment

ID: 13464227
It is in your SBS setup.  You probably have not set the logins to be permanent or not expire.  SBS has some ridiculous defaults on login duration, DHCP renewals, and timings that don't make sense.  Without taking many pages to walk you through all screens (I don't have SBS in front of me anyway), just explore all the user login, permissions, and expiry time and renewal settings, even on DHCP leases -- you will find one set to 6.00 p.m. every day.  So set it to NEVER expire, and the problem goes away, as long as you can find it!

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LVL 12

Expert Comment

ID: 13464685
I agree with sciwriter, it sure sounds like the DHCP lease expire.  Although Time To Live could also be coming from your ISP.

Check upstream and downstream with:

dig <any relevant hostname.domain.type or IP Address within your network>

The first nubmer should be the time to live.  Otherwise, try to find your own DNS cache, DHCP Administrator, or whatever, if you have your own name servers and dhcp servers.

Author Comment

ID: 13464713
I have gone and checked.
my DHCP lease durations are unlimited
and user accoutns also not to expire + login times unrestricted.

Not sure if time to live is issue
LVL 23

Expert Comment

ID: 13464799
Nope, it is a settings issue, for certain.  Why not search the registry for 6.00 pm -- or 18:00 -- to see if that text string jumps out.  It probably won't, knowing MS, they will hex code it in the registry -- of course, just to make it that much harder to find.  After all, why make it easy?

Also search all the docs for "time"  -- you will eventually find it.
LVL 12

Accepted Solution

GinEric earned 1000 total points
ID: 13466983
The Registry is just going to contain the settings for the DHCP service and DNS service.

I have seen this problem come from a router, one that has built in DHCP.

The usual TTL is 86400 seconds, exactly one day.  So a lease expire for the Server itself would occur at the same time every day, like 6:00 A.M.  The TTL I was referring to is in the the DNS Servers in the Zone Files for the appropriate zones, both Forward and Reverse usually as the first line or Option:

$TTL 86400

before the record begins.

It;s also the second number in the timing, 86400 ; "Refresh 1 Day"

There is no doubt that that is what it is.  The delays to the clients and servers is most likely while the DNS is being refreshed.

Now, if you do a dig for your network, like :

dig myhostserver.mydomain.mytld

You'll see the refresh figures in the first number column, below that, your ISP Name Servers.

If you dig the ISP Name Servers you will see that their TTL is usually 1 week!  Or about 604800 at the start of the countdown.  Example, my ISP name servers are currently at 156345 and 160083; which means they'll refresh in about two days.

Probably around Monday morning, right before rush hour. After Maintenance and backup that goes on from Sunday evening til pre-dawn Monday morning.

This all makes sense, you see, from a large network perspective, and most DNS and other stuff acts the way large networks default things to act.  When you get a copy of Bind or something similar from Microsoft, they set the default values to what they generally use as a large network.

And most of their clients are set to refresh at exactly one day,throughout most of the world.

There are other questions that come to mind:

How large is your network?
How many servers?
How many clients?

Most important:

Do you use your own Name Servers?
If so, are they standalone?

How many routers amd type?

And why are users online at 6:00 A.M.?  Unless it's really resetting at 6:00 P.M., which indicates your last Server reboot went off around 6:00 P.M. and you never reset the DNS and DHCP Servers to synchronize at a more convenient hour, like 3:00 A.M. or 6:00 A.M.

I did read back and see that it was 6 at night, but I had assumed, most probably wrongly, that your server was syncronized in the A.M., not the P.M.

I will check our servers and see what they have in their DNS and DHCP, but it just looks too much like the $TTL 86400 of DNS to me.

And that value does get stored in the Registry, I forget where, but if I find it I'll let you know.

Have you tried to flush the DNS at an A.M. hour?  Like 3:00 A.M. or something?

ifconfig /flushdns

Your server really should handle the synchronization, unless you've turned it off or have prevented recursion between your network and your upstream provider; perhaps they are resetting you once a day, in which case, it's not going to show up in the Registry except as some countdown value from 86400.

They shouldn't be flushing a customer network that much unless you have a very small office network or something similar.

Start with a dig on your name servers and your ISP's name servers.  Do a dig from a client machine to see what value they get.

The logs are the Server logs, system, DNS, DHCP, and so on.  The event log should have something for that time too.

I'll be back after looking at a Windows Server.

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