Computer Browser - computers randomly not appearing/Map Drives disappear

I just recently noticed that not all computers - in fact just a few - are showing up on most computers (Win 7 Pro) including the servers (2008 R2 & 2012).  For some reason, they are all showing up intermittently on my computer now though not earlier - not sure what I did other than clean the netbios cache and turn on the 'FDRP' service.   Tried doing this on another computer though, and did not have same effect.  Network discovery is ON - always has been.

I noticed because I am setting up a new laptop on the domain and it will not retain manually defined mapped drives, and it deletes any network folder icons I put on the desktop after logging off (no sys maintenance going on, I checked).  

The only thing I can think of that may have changed is I did a firmware update on my sonicwall firewall last week.

No errors in event logs; no windows firewalls on; network discovery is on the PC's though disabled by default on the servers.  I can get to any computer with it's netbios name via '\\servername'  in brower or ping servername.  Where should I look?
DSpieglAsked:
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Esteban BlancoConnect With a Mentor PresidentCommented:
AWESOME!  

The PDC change is a big part of it because now there is no election since the PDC is going to be "big daddy."  Changing Hyper-V to dynamic makes life easier for sure.  The speed change I don't think will make a big difference because they should be fine on auto.  Easy way to test that is to change them back and see if anything breaks.  Re-registering DNS, well that is good but I think your issue was stale records with some network tweaks.

Would you mind awarding points?
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Esteban BlancoPresidentCommented:
What was in the firmware update?  Did you read the release notes to see if this could happen?  Did it start happening immediately after the firmware upgrade?

Can you also look at Windows logs (system specifically) to see if something is disconnecting?  This sounds like a network problem for sure.
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DSpieglAuthor Commented:
I have submitted a case to Sonicwall to find out.  Didn't notice immediately but didn't look either.  Also I did unplug the firewall for a few minutes to see if the computers came back to network places, but they didn't.

This morning my computer doesn't have all the computers either so it keeps going back and forth.  I found 3 of these errors in the event log of the PDC from yesterday -

The browser has forced an election on network \Device\NetBT_Tcpip_{7E04DD22-1EDD-49C0-B094-AFCD88FD7869} because a master browser was stopped.

That may have been me trying to troubleshoot yesterday.  Also notice that several services have been stopping and starting in the logs of 3 main servers, over a period of time - adobe flash player, etc.

Also - 4-6 events per month on the 2012 server - DNS event 8012, 8013.

I am going to look into these DNS events now,  But if you have any thoughts, I'm listening!
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DSpieglAuthor Commented:
Oh, also 4-6 events per month on that 2012 server - NetBT - a duplicate name has been detected on the TCP network.  I'll look into that as well.  

I was guessing I was getting that because I have 2 hyper-v virtual machines on that server and virtual network adapter...but maybe more to it...
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Esteban BlancoPresidentCommented:
Let me research. How is your domain configured (as far as DC's)?  Sounds like a machine somewhere is trying to take over a role.
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Esteban BlancoPresidentCommented:
Duplicate name is same machine name in the domain. Have you cleaned out your computers OU?
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DSpieglAuthor Commented:
We have 4 physical servers and 4 virtual ones -

PDC - 2008 R2 and 2 virtual machines
BDC - 2008 R2
Other member servers - 1 2008 for content filtering and 1 2012 with 2 virtual machines

The AD list of computers is clean.  I just did DNS scavaging...

I am wondering if I have the NIC's set up correctly for the hyper-v machines.  Do you know how those should be set up?  I have Netbios settings and gateway settings that I am wondering about....
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Esteban BlancoPresidentCommented:
Yes. Tell me what you are wondering about on those settings.

The gateway settings have to be the same as the host if you don't have a separate subnet for the virtual machines.
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DSpieglAuthor Commented:
I had this 'working' but it's probably wrong.  I have 2 physical NIC's in the physical server.  I have an external virtual switch attached to both hyper-v servers.  This created a virtual ethernet adapter on my physical server.  Now I have - (representative ips)-

NIC1 - static ip 192.168.0.8; gateway 192.168.0.1; dns 192.168.0.6 (PDC)
NIC2 - is enabled as the hyper-v extensible virtual switch
Virtual switch ethernet adapter - static with gateway 192.168.0.1 ; dns 192.168.0.6

Then, for the network adapter on the virtual machine itself, I also have static ip -
192.168.0.12; gateway 192.168.0.1; dns 192.168.9.6

In other words, all network adapters with TCP/IP settings are (1) unique static; (2) same gateway and same dns.  It works but I'm sure that's not right!

Also, I have Netbios in the Wins settings - for the physical machine adapter it is on and the virtual switch adapter it is off.

I have tried to do this a miriad of ways but this was all I could get to work!  If I set up the virtual adapter to dynamic, it gets the same settings as I had only dynamic.  But when I set the network adapter on the virtual machine itself to dynamic, it gets nothing.
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Esteban BlancoPresidentCommented:
OK.  Let's take this from the top and organize.  Correct me please.

-You have one host that you use for Hyper-V.  This host contains two virtual machines.
-The host has two NIC's connected to the same physical switch.
-The domain controller is a physical box that is not the host.
-All your FSMO roles are in one domain controller.

Is this all accurate?
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DSpieglAuthor Commented:
Yes perfect!  (The domain controller also has 2 nics and 2 virtual machines but not important for sorting this part out at the moment).  

Also - since I commented last, I now have dynamic ip's on the virtual switch adapter of the hyper-v host and on the 2 virtuals themselves (in their network connections) and I am getting internet access from them.
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Esteban BlancoPresidentCommented:
Awesome.  Now, the host's IP addressing needs to be unique.  So the host should be (using fake IP addresses):

HOST (STATIC IP)
IP Address: 192.168.1.50
Subnet: 255.255.255.0
Gateway: 192.168.1.1

Primary DNS: <IP Address of your DC>

VIRTUAL SWITCH IN HYPER-V
Leave it dynamic for now.  Then assign IP addresses to the two guests like you would assign them for the host itself:

GUEST 1 (STATIC IP)
IP Address: 192.168.1.51
Subnet: 255.255.255.0
Gateway: 192.168.1.1

Primary DNS: <IP Address of your DC>

GUEST 2 (STATIC IP)
IP Address: 192.168.1.52
Subnet: 255.255.255.0
Gateway: 192.168.1.1

Primary DNS: <IP Address of your DC>

Your regular machines you can set a DHCP scope.  For example if you have 20 machines:
SCOPE from 192.168.1.70-90.

All machines of course need to be in the same domain.

Is that how you are set up?
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DSpieglAuthor Commented:
Yes
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Esteban BlancoPresidentCommented:
Have you looked in your domain controller in WINS to see if there are any thumb stoned records?
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DSpieglAuthor Commented:
I don't have any WINS running
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DSpieglAuthor Commented:
Hey, it seems fixed!  Here's the things I did -

- made virtual adapter on hyper-v hosts use dynamic ip rather than static
- DNS Scavenging
- del PTR in DNS and ipconfig /registerdns  (event log error 8012)
- changed speed of NIC's on hyper-v hosts to 100Mbps Full rather than auto
- turned Computer Browser service on for PDC (and file & print sharing on too)

Did a refresh on the network places on 4 computers/servers and everybody shows up!

Thanks - hope that's the end but will report back next week if not!
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DSpieglAuthor Commented:
Still having the problem with the laptop that originally alerted me to this issue.

Every time I log off and back on, I lose my mapped drive and shortcut to the folder on the mapped drive.  I will research this further and let you know.

Thanks for the help today!
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Esteban BlancoPresidentCommented:
You are most welcome.  Have you tried removing the drivers for the NIC on the laptop?  Maybe take it out of the domain, clear the computer from AD and re-join it.

Esteban
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