For the past two years, at random for different users, the connection to our SBS server breaks - the user sees an icon in the system tray saying that the server is unavailable. But it is fine for everyone else at that time and all other network connections are fine. If he immediately pings the server, it responds - so the network connection is fine.
To get the connection back, he needs to "Synchronise" with the server, and it always succeeds.
All PCs are set to synchronise files on logout - not on a timed basis.
I replaced the switches (now they are 3COM mostly Gb) and set up VLANs to try and segment the traffic, but it had no effect. During the two years, I also changed the firewall (Sonicwall -> Watchguard), the antivirus (McAfee -> Sonicwall) and the wireless LAN (US Robotics -> ZyXel).
It happens to about 10% of my users (5), 2 have laptops, 3 have desktops.
By "disconnect" I mean that in Windows Explorer you can no longer see the network drives (because the previous system was Netware 5, the users see shares on the network as drive letters)
We don't use ISA server.
Nothing appears in the server logs, I never thought of checking the client logs, I'll do that next time the problem occurs.
The clients are running Windows XP SP3 with automatic updates turned on. The server is also up to date on updates. The problem happens with both wired and wireless, I think we have seen less of the problem since I moved to 3Com 4200G gigabit switches, but it is hard to be sure - most people have stopped complaining, but it happened to me three times today
There are loads of items in the event log I don't understand, but none at the time of the disconnection. Except in the security log, where there are three or four items every second. Most along the lines of:
Logon attempt by: MICROSOFT_AUTHENTICATION_PACKAGE_V1_0 Logon account: Administrator Source Workstation: SBSSRV Error Code: 0x0 and User Logoff: User Name: SBSSRV$ Domain: CYLON Logon ID: (0x0,0x7D431B) Logon Type: 3
the switch claims there are no errors on the port my PC is connected to. How do I measure ICMP loss?