Hi,
Within client machine, I am able to ping the domain's IP like

C:\Users\peter>ping 192.255.10.21

Pinging 192.255.10.21 with 32 bytes of data:
Reply from 192.255.10.21: bytes=32 time=4ms TTL=126
Reply from 192.255.10.21: bytes=32 time=1ms TTL=126
Reply from 192.255.10.21: bytes=32 time<1ms TTL=126
Reply from 192.255.10.21: bytes=32 time=1ms TTL=126

Ping statistics for 192.255.10.21:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 0ms, Maximum = 4ms, Average = 1ms
    
and I also have put this


to IPv4 of the client, but when joining to the domain, I get this

First, try using NSlookup to check that you resolve A and SRV records :
http://social.technet.microsoft.com/wiki/contents/articles/29184.nslookup-for-beginners.aspx
http://support.microsoft.com/kb/241515

You can also check that your DCs are IP settings are well configured. You can find my recommendations here: http://www.ahmedmalek.com/web/fr/articles.asp?artid=24

DNS registration of your DCs can be forced by running ipconfig /registerdns and by restarting netlogon service.

Hi,
Thanks a lot.

I run this

C:\Users\peter>nslookup
DNS request timed out.
    timeout was 2 seconds.
Default Server:  UnKnown
Address:  192.255.10.21

> tst220750a.com
Server:  UnKnown
Address:  192.255.10.21

DNS request timed out.
    timeout was 2 seconds.
DNS request timed out.
    timeout was 2 seconds.
Name:    tst220750a.com
Addresses:  2002:c0ff:a15::c0ff:a15
          192.255.10.21

and have restarted Netlogon service on server,

and also have run this

C:\Users\peter>ipconfig /registerdns

Windows IP Configuration

Registration of the DNS resource records for all adapters of this computer has b
een initiated. Any errors will be reported in the Event Viewer in 15 minutes.

but I still get this