I’ve had a very long standing problem where mapped drives on Windows PCs are shown as disconnected after a PC wakes from sleep or after a reboot. Clicking to open the drive results in a delay of several seconds and then the share opens. I had this problem with Windows 7 right through to Windows 10 1909. Today, thanks to a different issue, I finally cracked it.
The problem is caused by Microsoft’s out-dated NetBIOS name resolution system. I (like most people) map drives to the name of the target server, and with “shortnames” (i.e. names without a domain after them) it seems like Windows tries to resolve the name with something other than DNS.
I discovered that disabling NetBIOS manually (see how below) meant that network drives were connected correctly after a reboot. I realised that if I could disable NetBIOS via DHCP i could fix all the PCs on my network with very little trouble. I tested this (instructions below) and was again successful!
- right click on the networking icon in the system tray
- “Open Network & Internet Settings”
- “Change Adapter Options”
- Right click on the relevant connection and select properties
- Double click on “Internet Protocol version 4 (TCP/IPv4)”
- Click on “Advanced…”
- Click on the “WINS” tab
- Untick “Enable LMHOSTS Look-up”
- Select the radio box for “Disable NetBIOS over TCP/IP”
Disabling via DHCP
- This will depend on your DHCP system — mine is a pfsense router
- In the DHCP Options set option 43
- On my pfsense box this is set to a string with a value of 01:04:00:00:00:02
- On a sonicwall box I found the type was set to “bytevalue” and I had to use a slightly different format which was 0x01;0x04;0x00;0x00;0x00;0x02
- In both instances we are effectively setting the same value which I believe is a hex. Notice that both have 6 “bits” with the values 1,4,0,0,0,2. For different systems I found a quick google will provide the appropriate format
- Delete the previous IP lease on the DHCP system, and then do an “ipconfig /release” “ipconfig /renew” (2 separate commands) on the client
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