New DC - dcdiag error - DCOM was unable to communicate with the computer...

[TwistedHelixis]

New promoted 2019 DC, getting the following error from dcdiag

 

An error event occurred. EventID: 0x0000272C Time Generated: 11/13/2022 10:09:27 Event String: DCOM was unable to communicate with the computer xx.xxx.x.x using any of the configured protocols; requested by PID 12b8 (C:\Windows\system32\dcdiag.exe), while activating CLSID {8BC3F05E-D86B-11D0-A075-00C04FB68820}.

The IP is a forwarding IP xx.xxx.x.x given to us by our LA. The IP is in the DNS forwarders on both old and new DC

 

If I run dcdiag on the older DC (2021r2) I don't get any errors.

 

Any help would be really great.

[TwistedHelixis]

not getting anywhere with Google. most of the posts are about using 8.8.8.8 as a forwarder on a DC, which is not the issue for me.

[psydii]

Just checking, but the DCs should be using themselves as DNS Servers and not the LA address, which should only be set in DNS Service MMC. Is this how you have it?

 

TBH not sure why DCOM would be trying to contact a DNS server, that's the job of other parts of the stack, perhaps something in the DNS Service configuration (via the DNS MMC) is off and the domain is resolving to the LA IP?

[HPlum78]

Just want to verify where you are now, so now you have two Domain Controllers and I guess you have pointed the original DC at the new DC as its primary DNS server then at its loopback address for its secondary address and the opposite way round for the new DC?

[TwistedHelixis]

Just checking, but the DCs should be using themselves as DNS Servers and not the LA address, which should only be set in DNS Service MMC. Is this how you have it?

Yes, the NICS primary / secondary IPs are the new & old DC IPs. The IP listed in the DCOM error is only entered in DNS > Domain > Properties > Forwarders

 

 

TBH not sure why DCOM would be trying to contact a DNS server, that's the job of other parts of the stack, perhaps something in the DNS Service configuration (via the DNS MMC) is off and the domain is resolving to the LA IP?

Not sure but I know from reading other posts that it is common for DCDIAG to give this DCOM error if Google's 8.8.8.8 DNS has been entered as a forwarder. If there is something off with DNS on the new server I haven't got a clue where to start as all the settings look the same for both servers.]

Ill go back through DNS tomorrow, just in case I have missed something.

 

 

Just want to verify where you are now, so now you have two Domain Controllers and I guess you have pointed the original DC at the new DC as its primary DNS server then at its loopback address for its secondary address and the opposite way round for the new DC?

Yes two domain controllers.

 

Old DC NIC DNS

Primary = looback

Secondary = New DC

 

New NIC DNS

Primary = Old DC

Secondary = loopback

 

The reason I have not set the old DC NIC to point at the new server for its primary, and its secondary as loopback yet, is I normally want a clean DCDIAG before switching those around. Also in this case the DCDIAG error is from the new server, which is using the old DC as its primary, so just assumed (could be wrong) that that was not the issue.

Edited November 13, 2022 by TwistedHelixis

[TwistedHelixis]

UPDATE: Just been told by the LA that the forwarder IP's are being (have been) decommissioned and I need to use 8.8.8.8. Not sure why the old server didn't report any issues when I ran DCDIAG but ha ho.