Question : Non existent domain when doing an nslookup to second domain

I have recently build a new WIndows Forest/Domain with a single domain controller which is Windows Server 2003 SP2. I ran dcpromo to install AD on the box and allowed the wizard to create the DNS automatically.
When i look in DNS console i see under forward lookup zones - domain name, the _msdcs folder is greyed out, not sure why. Suppose this is the first issue.
 Everything else in DNS looks correct, dynamic updates are set to 'nonsecure and secure' and the name server is the name of my domain controller. The NS record for the domain controller is also present.
When i do an nslookup for the domain name, server or IP for the domain controller again it looks fine.

I have a second Windows Forest/Domain which has been establised for a few years now again all DCs in this domain are Windows server 2003. The purpose of building the new domain above is to establish a 2 way fully transitive forest trust between the two domains. Both forests exist on the same VLAN so there are no firewall rules in play here.
When i do an nslookup from the new domain to the old domain it all looks fine. It displays the IPs for all the DCs in the old domain and the fully qualified name of the old domain so again all looks good.
When i attempt an nslookup from the old domain to the new domain i get the error message 'cannot find the new domain: Non existent domain'. This is preventing me from establishing the trust.

Apologies if the above description is a little messy and all over the place. I don't know what else to try on this and would greatly appreciate any help.

Answer : Non existent domain when doing an nslookup to second domain

Make sure you are DNS Forwarding to the other domain or create a secondary zone for each domain on the other DNS server