I'm also having the same problem joining Clearpass to the domain.
ClearPass Policy Manager 6.5.1.72346 on CP-VA-25K platform
The domain controller is the primary DNS server.
The clock is set to NTP using the domain controller as the NTP server. Double-checked and the time between the two is spot on.
NSlookup does return the domain controller:
[appadmin@cppm01]# network nslookup -q host dc01.local.customer.ca
unknown query type: HOST
Server: 10.10.10.3
Address: 10.10.10.3#53
Name: dc01.local.customer.ca
Address: 10.10.10.3
We are using a Domain Admin account. But no matter what we try, the results are the same:
Adding host to AD domain...
INFO - Fetched REALM 'LOCAL.CUSTOMER.CA' from domain FQDN
'dc01.local.customer.ca'
INFO - Fetched the NETBIOS name 'CC'
INFO - Creating domain directories for 'CC'
Enter da1's password:
Failed to join domain: failed to lookup DC info for domain
'LOCAL.CUSTOMER.CA' over rpc: NT_STATUS_CONNECTION_RESET
INFO - Restoring smb configuration
INFO - Restoring krb5 configuration file
INFO - Deleting domain directories for 'CC'
ERROR - cppm01 failed to join the domain LOCAL.CUSTOMER.CA
with domain controller as dc01.local.customer.ca
Join domain failed
The only thing I can't do is use the default "Administrator" account because they have renamed it on their domain.