What are the higher ports needed by RPC to successfully join the domain?

I have an extermal site which is connected to our corporate network via a firewall. According to the Microsoft KB, all higher ports from 1024 to 65535 need to be opened in order to join the domain successfully. Currently, i am hit with an error "There are no more endpoints available from the endpoint mapper." However, due to security consideration, the network team do not wish to open all higher ports but requested what are the specific higher ports to be opened? Are there any specific high ports for RPC? I dont think so.. Normally, what is the best practice to approach this problem? Does anyone of you have faced this situation? Thanks in advance.