Unable to join the domain?

I am having difficulties in joining my Windows Server to the domain, may I know what could be the problem ?

I suspect that there is a firewall in between this DR internal site and the DMZ where this Forefront TMG 2010 is deployed ?

DCDiag /s: result:

Directory Server Diagnosis

Performing initial setup:
   [DCDNS01.domain.com] LDAP bind failed with error 1326,
   Win32 Error 1326.
   Server DCDNS01.domain.com resolved to these IP addresses: 192.168.127.10,
   but none of the addresses could be reached (pinged). Please check the
   network.
   Error: 0x2b02 "Win32 Error 11010"
   This error more often means that the targeted server is shutdown or
   disconnected from the network.

ok, from the portqry I get the following result while the rest with exits with return code 0x00000000 means that is OK ? so why there are some with Exit code 1 and 2 ?

UDP port 389 (unknown service): LISTENING or FILTERED

Using ephemeral source port
Sending LDAP query to UDP port 389...

LDAP query to port 389 failed
Server did not respond to LDAP query

portqry.exe -n 192.168.12.5 -e 389 -p BOTH exits with return code 0x00000001.
=============================================

 Starting portqry.exe -n 192.168.12.5 -e 53 -p BOTH ...


Querying target system called:

 192.168.12.5

Attempting to resolve IP address to a name...


IP address resolved to DR-DCDNS01-vm.domain.com

querying...

TCP port 53 (domain service): LISTENING

UDP port 53 (domain service): LISTENING or FILTERED

Sending DNS query to UDP port 53...

DNS query timed out
portqry.exe -n 192.168.12.5 -e 53 -p BOTH exits with return code 0x00000002.
=============================================

 Starting portqry.exe -n 192.168.12.5 -e 88 -p BOTH ...


Querying target system called:

 192.168.12.5

Attempting to resolve IP address to a name...


IP address resolved to DR-DCDNS01-vm.domain.com

querying...

TCP port 88 (kerberos service): LISTENING

UDP port 88 (kerberos service): LISTENING or FILTERED
portqry.exe -n 192.168.12.5 -e 88 -p BOTH exits with return code 0x00000002.
=============================================

 Starting portqry.exe -n 192.168.12.5 -e 138 -p UDP ...


Querying target system called:

 192.168.12.5

Attempting to resolve IP address to a name...


IP address resolved to DR-DCDNS01-vm.domain.com

querying...

UDP port 138 (netbios-dgm service): LISTENING or FILTERED
portqry.exe -n 192.168.12.5 -e 138 -p UDP exits with return code 0x00000002.
=============================================

 Starting portqry.exe -n 192.168.12.5 -e 42 -p TCP ...


Querying target system called:

 192.168.12.5

Attempting to resolve IP address to a name...


IP address resolved to DR-DCDNS01-vm.domain.com

querying...

TCP port 42 (nameserver service): FILTERED
portqry.exe -n 192.168.12.5 -e 42 -p TCP exits with return code 0x00000002.

any kind of help would be greatly appreciated.

If there is a firewall between the host server and your domain controllers, you will need to ensure it is configured to allow applicable traffic to pass between them. Microsoft have a KB on what's needed:

http://support.microsoft.com/kb/179442