Question : Random network crashes in domain...

Hello,
We have recently began to experience a severe issue within our network.  The issue happens very randomly (it could be as infrequent as once every 2 or 3 weeks, or it could be 2 weeks consecutively).  The issue is that ALL network functionality on ALL machines (servers, workstations, IP phones, etc...) completely ceases for 5 - 7 minutes before the problem clears itself and network connectivity is restored.  Please note, I can ping the loopback address, but no other addresses (DNS or the Default Gatway).  I have done this on multiple machines to verify.  Previously I noted that there were MRxSmb 8003 errors appearing on a secondary DC coming from our PDC so I disabled the Computer Browser service on all DC's and member servers (note that I did not modify the registries of any server).  Unfortunately, there is nothing in the Event Viewer on any machine for the most recent issue that occured (7:30pm MST), except for a WINS error that it was unable to replicate during the issue.

There are 2 DC's and 8 Member Servers as well as 70 W2K clients and 70 XP Pro boxes.  We are using a DLINK DFL 800 NetDefend firewall/VPN appliance.

This problem is driving me absolutely bonkers!  Any help or suggestions would be greatly appreciated.  Please let me know if you need any additional inforamtion.

Answer : Random network crashes in domain...

You won't find event log errors in the DC. This is a conflict on how packets are routed over the switches and routers to the outside world.  

The symptoms you are describing, I have seen on two different occasions:

1) we had multiple connections, (lets say two ethernet connections), between a remote switch and a backbone switch. In that case, just the remote switch kept loosing intermittently crashing.

2) the second problem was the router was conflicting with another router and the packets didn't know the default route for routing packets. The gateways of the routers needed to be set to the gateway of the enterprise router, (WAN router in your case). It's an easy test to UNPLUG all routers except your WAN router to see if the interference is there.

This sounds like multiple connections between switches, or a router conflict.

It isn't consistent with a domain controller problem.