DC replication issue DNS warning 4013

You can probably ignore this error if it happened once when you rebooted the server.

Otherwise, we need more info.

What version of Windows Servers are you running?

What operations did you do before the error appeared?

Which status code did you get? (https://support.microsoft.com/en-za/help/2001093/troubleshoot-dns-event-id-4013-the-dns-server-was-unable-to-load-ad-in) Also, track down for any reference to an old DC...

Can you post the results of "dcdiag /test:DNS" command?

DC holding FSMO roles and DNS is Win2008 R2

dcdiag /test:DNS

Directory Server Diagnosis

Performing initial setup:
   Trying to find home server...
   Home Server = DC
   * Identified AD Forest.
   Done gathering initial info.

Doing initial required tests

   Testing server: Default-First-Site-Name\DC
      Starting test: Connectivity
         ......................... DC passed test Connectivity

Doing primary tests

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

      Starting test: DNS

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

   Running enterprise tests on : XYZ.net
      Starting test: DNS
         ......................... XYZ.net passed test DNS


On Additional Dc teh results are as follows,

Performing initial setup:
   Trying to find home server...
   Home Server = DC01
   The directory service on DC01 has not finished initializing.
    In order for the directory service to consider itself synchronized, it must
   attempt an initial synchronization with at least one replica of this
   server's writeable domain.  It must also obtain Rid information from the Rid
   FSMO holder.
    The directory service has not signalled the event which lets other services
   know that it is ready to accept requests. Services such as the Key
   Distribution Center, Intersite Messaging Service, and NetLogon will not
   consider this system as an eligible domain controller.
   * Identified AD Forest.
   The directory service on DC01 has not finished initializing.
    In order for the directory service to consider itself synchronized, it must
   attempt an initial synchronization with at least one replica of this
   server's writeable domain.  It must also obtain Rid information from the Rid
   FSMO holder.
    The directory service has not signalled the event which lets other services
   know that it is ready to accept requests. Services such as the Key
   Distribution Center, Intersite Messaging Service, and NetLogon will not
   consider this system as an eligible domain controller.
   Done gathering initial info.

Doing initial required tests

   Testing server: Default-First-Site-Name\DC01
      Starting test: Connectivity
         The directory service on DC01 has not finished initializing.
          In order for the directory service to consider itself synchronized,
         it must attempt an initial synchronization with at least one replica
         of this server's writeable domain.  It must also obtain Rid
         information from the Rid FSMO holder.
          The directory service has not signalled the event which lets other
         services know that it is ready to accept requests. Services such as
         the Key Distribution Center, Intersite Messaging Service, and NetLogon
         will not consider this system as an eligible domain controller.
         ......................... DC01 passed test Connectivity

Doing primary tests

   Testing server: Default-First-Site-Name\DC01

      Starting test: DNS

         DNS Tests are running and not hung. Please wait a few minutes...
         ......................... DC01 failed 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 : xyz

   Running enterprise tests on : xyz.net
      Starting test: DNS
         Test results for domain controllers:

            DC: DC01.xyz.net
            Domain: xyz.net


               TEST: Basic (Basc)
                  Warning: adapter
                  [00000010] Intel(R) 82574L Gigabit Network Connection has
                  invalid DNS server: 127.0.0.1 (DC01)
                  Warning: no DNS RPC connectivity (error or non Microsoft DNS s
erver is running)

         Summary of test results for DNS servers used by the above domain
         controllers:

            DNS server: 172.25.1.55 (DC01)
               1 test failure on this DNS server
               PTR record query for the 1.0.0.127.in-addr.arpa. failed on the DN
S server 172.25.1.55               Name resolution is not functional. _ldap._tcp
.xyz.net. failed on the DNS server 172.25.1.55

               DC01                         PASS WARN n/a  n/a  n/a  n/a  n/a
         ......................... xyz.net passed test DNS

Additional DC is Win 2012 R2 server

Can you run repadmin /showrepl * (including the asterisk) on one of the DCs and post the output here?

Is your DNS service even running? Can you restart the service?

Can you open the DNS console and check DNS settings? Check your DNS records for your DNS servers in a console and check DNS settings on the NIC.