Firstly, I'll admit that my networking knowledge is limited so as people request more information I'll update this question accordingly.
I am trying to create a NLB Cluster across 2 Windows Server 2008 Web Servers. Neither of the machines are members of a domain, and both have 2 NICs (one for processing external web traffic, and one for communicating internally).
I have installed NLB on both machines, and have created a cluster on Host A and added itself to it. However, when I try and add Host B (using the address from the external NIC) I get the following error : "The RPC server is unavailable on the specified computer".
On Host B I can see that the RPC service is running fine. I can also ping and RDP from Host A to Host B with no problems either. I have disabled the windows firewall on both machines but that had no effect