unable to resolve hostname during ESXi installation

I am just setting up vSphere and ESXi into a small virtual network [within vm workstation]. 

Set up a static IP for the ESXi hypervisor, entered the DNS/Gateway but it is unable to resolve the hostname when I 'test management network'. 

The ping to the DNS server works.

Ping to the default gateway works.

Resolving the hostname does not.

I added the ESXi static IP, hostname and selected update PTR record within DNS on the pri DC.

I can ping the ESXi address and hostname from the DC and other work stations on the virtual network.

I can nslookup the IP address that I am putting ESXi on.

But yet, I cannot get the 'testing management network' to resolve the hostname.

Any ideas?

Thanks.