Windows 2008 R2 nslookup does not resolve ../etc/hosts but ping does

I have a strange problem my server has 2 network one for production the one connect to AD, DNS and other for backup, we use our standard name server-bck,  for the server-bck I put only  in the c:\windows\system32\drivers\etc\hosts file not in the DNS server

Strange thing if I ping server-bck it can resolve to the IP, but if  I do the nslookup server-bck, it won't resolve anything, but nslookup will resolve anything on our DNS server.

Anyone know the answer?

Thank you.
Iwan Tamimi