Recently we have been experiencing power cuts problems at our building. When power is off for longer than 10 minutes all UPS go off and hence all the servers, switches, routers etc.
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: When power comes back on (after being off for like 15 minutes or so) and all devices turn on at the same time...the network seems not be working. We troubleshoot and realise one of the switch is not working...meaning all users connected to it are offline. However, if move all the users from the non-working switch to the working switch they all get connected online. At first, I thought the switch is broken...only to realise if I move the server and router (gateway to the internet) to the broken switch and add some users on it; these users all get connected. By doing this I managed to narrow it down as follows: All users connected to FIRST, SINGLE switch where Gateway and Server are connected can reach the Server and the Internet. But, if I connect a SECOND switch to the FIRST switch with a patch cable; all users on the SECOND switch are continue to get stay Offline. The situation repeat when I connects servers and gateway to the second switch then join it with the first switch.
We manage to identify a bad cable every time when this happen. So, I thought the problem is that particular cable...I isolate the cable, only to realise after couple of days when power goes out and come back, the same problem re-appear. Then I find another bad cable and isolate it. However, at this time when I plugged in the old bad cable is working very fine!! So, bad cable today turns out to be good cable after couple of days...and situation keep repeating. The source of the problems keep changing.
We would come in the morning to find everything is working perfectly, then around lunch time electricity goes...when it comes back network starts to misbehave!!. I am puzzled as to why this ONLY happens when Electricity go off...if it is a network loop shouldn't be causing problems all the time?