Microsoft Network not working!


Please assist...we have had the network connected and working without a glitch for the past 3 years...then all of a sudden couple of days ago the whole network stopped working.

Set up is like this: We have Server running Ms Windows server 2003 and other small applications like ms access database, active directory etc. We also use this server as a file server. The server is connected to total of 4 D-Link 1024 switches, the client computers then connects to these switches...(flat network). All the client computers access the server this way. These four d-link switches are connected up using a patch cable that run from one switch to another...on some of the switch ports we have connected a total of 8 Wireless Access Points (mix of D-Links and Zyxel). That is how our network is set up...

The problem: It started as a slowness on the network, then followed by some of the access points not working. We troubleshoot and realise if we disconnect some of the access points the switches start working, so we isolated 3 access points. This solved the problem only temporarily, after 2 hours we were back to square one: the access points that we thought are causing the problem are not the problem anymore!! It is as if the problem has now moved to something else...if we disconnect a number of users everything works well for a short while before the problem reappear with other is like the source of the problems keep changing.

Please assist what are the possible issues that can cause this from happening.

Thank you.
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gt2847cSr. Security ConsultantCommented:
If you leave the APs disconnected, does the problem reoccur on the wired only network?

Are you able to isolate the APs to one switch only? (not sure of your physical layout).

How are your switches connected?  Serially, star, ???  Is there a possibility you have a loop in your network?

Do the activity lights on your switches show unusual amounts of traffic on any (or all) ports?

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TMAAAuthor Commented:

Yes, if I leave APs disconnected the problem re-occur on the wired network.

I have isolate the APs to one switch and the problem reoccur on another wired device, disconnected that and it reoccur on another one.

My switches are connected serially. I will investigate a loop...

I can not say the lights are working overtime, I need to pay more attention to them....

Is there an easy way to troubleshoot a loop in the network?


We had a loop problem on the network, and it start like yours slow access, ping lost 3 of 4 etc.
we had 4 3Com swiches on teamand all ligths were ON or all flashing.
We diagnose that by switching off all switches and starting one by one with 10 min interval.
When we found the guilty switch we disconnect all cables and connected one by one all 24.
The problems was one port where we found another small unmanaged switch with a loop on it (one cable connected to two ports).
That take us 1/2 day we want to kill the user, but never find him.
So try follow the same path (except kill user).

gt2847cSr. Security ConsultantCommented:
If you have a loop, the activity switches will typically go to a solid/always on due to the broadcast storm it generates.  

Without having managed switches, the easiest way to track down a loop (and a number of other problems) is by isolating portions of the network.  With how you described your connection, disconnect the patch cables from between the switches and see if you can find which switch is misbehaving.  If the problem goes completely away, it becomes a little more difficult as you may have a loop between switches rather than on the same switch (one port on switch A, a second on switch B).

If you isolate the problem to one switch, start disconnecting ports to see if clears up.  You'll want to give it a few moments between disconnects as the broadcast storm will take a few moments to subside.  If you find the offending port, track down where it's patched to and see whats on the other end.  I've seen everything from desktop switches multiply connected to the wall and IP phones with pass through ethernet ports with both ports connected to the wall (sometimes you have to wonder what people are thinking when they do stuff like that - goes faster with more ports???).

If the problem subsides when the switches are isolated, then you'll have to reconnect switches one at a time to see when the problem starts back up.  With it distributed across multiple switches, the broadcast storm will take longer to ramp up, so you'll need to be patient while doing this.  Allow a bit of time in between connections to see if it starts up.

As you have not described your physical layout (everything in one closet or distributed around the building), it's a bit harder to give you more specific advice, but the above should give you a start on it.  Even if it's not a loop, isolating the network pieces can also help sort out misbehaving ethernet cards/workstations, etc.
TMAAAuthor Commented:
Thank you for very useful advice. I managed to find a small D-Link switch with two ports connected to the same. To my surprise it is our very own Electrician who did this!!!

Though, I am confident that this must have been the problem. It is a weekend today, come Tuesday when most of the staff will be in the office. I will know for sure.

Thanks ever so much.
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