Domain controller malfunction

Question

We have one domain and two domain controllers (on Windows Server 2008 Enterprise).

For about a week, we have enormous problems: some users can't log in to Windows (domain could not be contacted). Sometimes restart of Windows helps, but mostly it doesn't.

As administrator, I can't log in to DC0, on DC1 I can. The other administrator for example can log in to both DC.

I attached dcdiag /test:dns for both DC0. DC0:

 Directory Server Diagnosis


 Performing initial setup:

Trying to find home server...

 Home Server = DC0

* Identified AD Forest. 
  Done gathering initial info.


 Doing initial required tests


 Testing server: Default-First-Site-Name\DC0

  Starting test: Connectivity

     ......................... DC0 passed test Connectivity

Doing primary tests


Testing server: Default-First-Site-Name\DC0


  Starting test: DNS



     DNS Tests are running and not hung. Please wait a few minutes...

     ......................... DC0 passed test DNS


 Running partition tests on : ForestDnsZones


 Running partition tests on : DomainDnsZones


 Running partition tests on : Schema


 Running partition tests on : Configuration


 Running partition tests on : our_domain


 Running enterprise tests on : our_domain.si

  Starting test: DNS

     Test results for domain controllers:


        DC: DC0.our_domain.si

        Domain: our_domain.si




           TEST: Records registration (RReg)
              Network Adapter

              [00000006] Intel(R) PRO/1000 MT Network Connection:

                 Warning: 
                 Missing AAAA record at DNS server 193.77.60.214: 
                 gc._msdcs.our_domain.si

           Warning: Record Registrations not found in some network adapters


           DC0                          PASS PASS PASS PASS PASS WARN n/a  
     ......................... our_domain.si passed test DNS

DC1:

 Directory Server Diagnosis
 Performing initial setup:

 Trying to find home server...

 Home Server = DC1

 * Identified AD Forest. 
 Done gathering initial info.


 Doing initial required tests


  Testing server: Default-First-Site-Name\DC1

  Starting test: Connectivity

     ......................... DC1 passed test Connectivity



 Doing primary tests


  Testing server: Default-First-Site-Name\DC1


  Starting test: DNS



     DNS Tests are running and not hung. Please wait a few minutes...

     ......................... DC1 passed test DNS


 Running partition tests on : ForestDnsZones


 Running partition tests on : DomainDnsZones


 Running partition tests on : Schema


 Running partition tests on : Configuration


 Running partition tests on : our_domain


 Running enterprise tests on : our_domain.si

  Starting test: DNS

     Test results for domain controllers:


        DC: DC1.our_domain.si

        Domain: our_domain.si




           TEST: Dynamic update (Dyn)
              Warning: Failed to add the test record _dcdiag_test_record in zone our_domain.si

           TEST: Records registration (RReg)
              Network Adapter

              [00000006] Intel(R) PRO/1000 MT Network Connection:

                 Warning: 
                 Missing AAAA record at DNS server 193.77.60.213: 
                 DC1.our_domain.si

                 Warning: 
                 Missing AAAA record at DNS server 193.77.60.213: 
                 gc._msdcs.our_domain.si

                 Warning: 
                 Missing AAAA record at DNS server 193.77.60.214: 
                 DC1.our_domain.si

                 Warning: 
                 Missing AAAA record at DNS server 193.77.60.214: 
                 gc._msdcs.our_domain.si

           Warning: Record Registrations not found in some network adapters


           DC1                          PASS PASS PASS PASS WARN WARN n/a  
     ......................... our_domain.si passed test DNS

Here are IP's for DC0 and DC1 - they are all right (why there are so many?):

Here is 'ipconfig /all' on DC0:

Answer 1

There are a couple of glaring problems here:

1. Your Domain Controller that you've screen shotted is multi-homed. This is a problem. There is usually not a good reason to do this and there are special consideration to take in regards to DNS registration, etc. Have you followed these? I'm assuming not. Really consider redesigning your network to not multihome your DCs.

2. Your DCs are using themselves first for DNS resolution. This can lead to a replication island like you're experiencing. They should use each other first and themselves (127.0.0.1) second.

3. That 193 address that you've provided is a publicly routable IP. There is absolutely no reason that a Domain Controller should be Internet accessible. This in and of itself isn't going to break what you're seeing, but it's a huge security issue that you should fix asap.

Answer 2

Ok, so as the comment conversation looked to be going on forever, I will instead post what I believe the problem is:

Although it looks initially like an issue with DC0, it is actually an issue with replication between the two controllers and, as such, the problematic controller is DC1.

The easiest option open to you will be to shutdown DC1 and build a 3rd domain controller, DC2, then change secondary DNS settings on all servers and DHCP scopes to point to this server.

So long as you then have a stable domain I would suggest deleting DC1 from the domain and leaving it at that, any changes you have made on DC1 since it has last replicated will be lost, this includes users' password changes and new user accounts, so it will require some cleanup on your part, but if you can't fix the replication issue yourself (which, no offence meant, I don't believe you're capable of) this is the easiest way to resolve your problems.

If, on the other hand, you add DC2 with DC1 offline and are still having issues, I advise you seek assistance from a local Microsoft Professional.

Answer 3

(This is only a partial answer to one of your side questions...)

For some reason your DCs have 6to4 addresses. If you're sure you aren't using 6to4 (you probably aren't) then you should probably disable it.

netsh interface ipv6 6to4 set state disabled
netsh interface teredo set state disabled