Replaced 2008 DC, now remote systems are slow to browse network

Question

I just replaced our DC that also served as one of several DNS servers.  All FSMO roles were transferred to the new DC before demoting.
After doing so, the majority of our remote sites (connected via site-to-site VPN), can no longer access the UNC path of the file server also located in each remote site, and if they can, it is extremely slow.  However, this isn't happening to every
remote site.  Affected sites are also unable to access UNC path via IP address, although nslookup/pings resolve normally.  The temporary workaround is to remove all affected systems from the domain.  As soon as those machines are removed from
the domain and rebooted, accessibility to these paths returns instantly.

Answer 1

What did you replace your 2008 DCs with?
Are you using WINS?
Transferring FSMOs wouldn't have anything to do with this. FSMOs are operational role holders that perform tasks for the domain and forest, and do not have anything to do with speed or authentication. However, I've seen slowness occur due to authentication
issues, especially with older operating systems and apps.
I've also seen issues with the TCP Chimney that can cause slowness.
TCP Chimney and RSS Feature May Cause Slow File Transfers or Cause Connectivity Problems
Published by Ace Fekay, MCT, MVP DS on Aug 20, 2009 at 12:44 AM, Updated 10/26/2014
http://blogs.msmvps.com/acefekay/2009/08/19/tcp-chimney-and-rss-features-may-cause-slow-file-transfers-or-cause-connectivity-problems/
And if you replaced the DCs with 2012 or newer, you will also want to inventory your applications to make sure that nothing is using NTLM v1 or LANMAN, which no longer be supported in Windows 2012 R2.  So if you have any older apps that are using the
older authentication methods, they may no longer work.
More info:
Understanding Active Directory Domain Services (AD DS) Functional Levels
http://technet.microsoft.com/en-us/library/understanding-active-directory-functional-levels(v=ws.10).aspx
Windows Server 2012 slow network/SMB/CIFS problem
http://jrs-s.net/2013/04/15/windows-server-2012-slow-networksmbcifs-problem/
Ace Fekay
MVP, MCT, MCSE 2012, MCITP EA & MCTS Windows 2008/R2, Exchange 2013, 2010 EA & 2007, MCSE & MCSA 2003/2000, MCSA Messaging 2003
Microsoft Certified Trainer
Microsoft MVP - Directory Services
Complete List of Technical Blogs: http://www.delawarecountycomputerconsulting.com/technicalblogs.php
This posting is provided AS-IS with no warranties or guarantees and confers no rights.