Domain workstations briefly losing internet at same time

After replacing a Windows 2003 Standard server with a Windows 2016 Essentials server,  I am getting no network errors from the server.  However, it seems almost once an hour the workstations lose network connectivity.  Checking their error logs the Dns server is timing out.  Causing the network connections to drop for all sites momentarily.  This is trouble some since they are trying to print large files off plotter printers, and it will cause those jobs to stop half way through.  I have ran a dcdiag /test:dns and found that is pointing to the new dc.  The tests are all successful I do not see any failed tests.  The forwarders point to googles.  No reverse lookup zone is present.  The DHCP server is the fortigate and that is giving everyone the DNS server's IP and only that.
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JohnBusiness Consultant (Owner)Commented:
Your server will do DC and AD services and so put DHCP and DNS on this server and remove from the Fortigate machine. This is a better (much better) way to do DHCP and DNS

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What roles are being handled by each server? Ideally, you would be able to get the 2003 server out of there.
Rob WilliamsCommented:
Make sure the workstations point to the new 2016 server for DNS, and only it.  Do not add an ISP or fortigate even as an alternate DNS server.
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dtc203Author Commented:
Well the 2003 server is being removed completely from the network.  At this moment all workstations are pointing to the new DNS server and not the 2003 server.  I will try to change where the DHCP server resides from the fortigate to the new server, and report how that is functioning.
And is it just the workstations losing connectivity? You may also want to look at the switch.
Rob WilliamsCommented:
>>"At this moment all workstations are pointing to the new DNS server and not the 2003 server. "
An no other alternate?  If you add an alternate other than a local domain DNS server you can experience timeouts and name resolution issues.
dtc203Author Commented:
Yes no other alternatives, Rob.
dtc203Author Commented:
So far after replacing the switch and changing the DHCP server to the Domain Controller, no more network drops.
JohnBusiness Consultant (Owner)Commented:
Thanks for the update and I am glad this solution worked for you.
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