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Windows 10 Peer-To-Peer problem

LockDown32
LockDown32 used Ask the Experts™
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It is a peer-to-peer network. 4 workstations. All Windows 10 Pro X64. The "Main" workstation had a shared Laserjet. Today they called and said none of the other three workstations could print. In looking around the problem seemed to be in the  main computer. Lo and Behold the network type switched from Private to Public which does ugly things to the firewall. Believing that was the problem I set it back to "Private". The other three still couldn't print. I rebooted all of them and still no shared printing. I deleted the printer from the three and tried to re-add it. Got Access Denied. What I had to do was re-share it on the main computer (simply turn off sharing for the printer and immediately turned it back on). Then I could re-add it to the other three workstations.

   So why does the network type change on the main computer and why did it completely destroy the sharing even after setting it back? Is there any way to "static" the network type so this doesn't keep happening? I know it happens on Domain Controller becaise the NLA service gets started before the DNS service but on a peer-to-peer this seems like a major flaw.....
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Systems Administrator
Commented:
Sounds like someone was messing with the main workstation.  How is it secured?  Is it in a secure room? Is protected by a login/password and if so, who has that login and password?  

You could try combining through the event logs to see if any changes were made, but in the meantime, you may want to load Sysmon (https://docs.microsoft.com/en-us/sysinternals/downloads/sysmon) to track any changes being done on the system from this point forward.
Distinguished Expert 2018

Commented:
The network type is set per NIC. So anything that creates a new NIC or resets the NIC will reset the type of network. This is *usually* a driver update where the vendor didn't test a driver upgrade scenario. But some other network changes can do this as well. Installing hyper-v or containers. Resetting the TCP/IP stack. Etc.
Distinguished Expert 2018

Commented:
I'll note that you don't see this in a domain usually because even when the NIC gets reset in a domain, it sees a domain controller so it selects the domain profile by default. But in a workgroup that can't happen so the user gets prompted.
LockDown32Owner
Top Expert 2016

Author

Commented:
So in a peer-to-peer network sharing is based on NIC and not computer name? Why wouldn't a simple reset of the network type back to "Private" re-establish shared resources?
Distinguished Expert 2018

Commented:
So in a peer-to-peer network sharing is based on NIC and not computer name?
Correct.

Why wouldn't a simple reset of the network type back to "Private" re-establish shared resources?
Because of all of the features that were disabled. Some cases, a reboot might help. This is something that could have probably been implemented better.
LockDown32Owner
Top Expert 2016

Author

Commented:
So I can change the computer name and it won't effect sharing since sharing is NIC based right?
Distinguished Expert 2018

Commented:
Right.
Is there any way to "static" the network type so this doesn't keep happening?

Yes, there is.
Using gpedit, go to
Computer Configuration
Windows Settings
Security Setting
Network List Manger Properties

Then you might change:
Unidentified Networks
and/or
Identifying Networks

A caveat:  you may not want to set laptops to "Private" unless you know what will happen in a coffee shop!