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Can't bind Macs to Active Directory, it's not time synchronization, what else could be wrong?

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Mac computers are unable to bind to our Windows Active Directory server. The error is the unhelpful Node name wasn't found (2000). Windows and Samba clients have no problem. All the systems on our LAN use our internal bind9 1:9.16.1-0ubuntu2.10 name server. Active Directory is running on Windows Server 2019

Almost all internet solutions recommend explicitly reconfiguring the AD server and the Mac clients to use Network Time Protocol (NTP), and to ensure that they are using the same time server. I did that, it did not solve the problem.

Many other user recommend not binding the Macs to AD at all, and to use NoMad instead. I tried NoMadLogin-AD, and that didn’t work either! That was a big clue. A help page for NoMad described that NoMad queried DNS for the ldap server, and further googling revealed that the there is a similar dig query: dig +short -t srv _ldap._tcp.your.domain.here. My result came back as

 0 0 289 melbourne.your.domain.here.

The LDAP port is supposed to be 389, not 289.

Score:0
in flag

The solution was to correct the port values for the AD service records of our DNS.

In our bind 9 config, we have 11 special Active Directory "site" files:

_msdcs.your.domain.here.hosts
_tcp.e6b6bf1d-0a16-4441-a066-32a59b46b65d.domains._msdcs.your.domain.here.hosts
_tcp.dc._msdcs.your.domain.here.hosts
_tcp.Default-First-Site-Name._sites.dc._msdcs.your.domain.here.hosts
_tcp.Default-First-Site-Name._sites.gc._msdcs.your.domain.here.hosts
_tcp.Default-First-Site-Name._sites.your.domain.here.hosts
_tcp.gc._msdcs.your.domain.here.hosts
_tcp.your.domain.here.hosts
_tcp.pdc._msdcs.your.domain.here.hosts
_udp.your.domain.here.hosts

8 of these files have LDAP SRV records, and in our case, all of them had the wrong LDAP port. I replaced all the 289 values with 389, and restarted the name server. Now the result from dig +short -t srv _ldap._tcp.your.domain.here is

 0 0 389 melbourne.your.domain.here.

And Macs are finally able to bind. I cannot explain why only the Macs are sensitive to the mis-configured DNS.

Our particular mis-configuration was a specific fault, but it is clear that DNS can be a problem for binding Macs to AD. So explore that when you are troubleshooting the dreaded Node name wasn't found (2000) error.

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