NATs and firewalls can impact the strategy by which your WCF clients and services communicate.
Use the following steps to determine WCF configuration for a NAT or firewall:
1. Determine the addressability of the service and client machines. If the service or the client are behind a NAT and are not directly addressable then use a technology such as Microsoft Teredo to enable communication.
2. Determine if there are protocol or port constraints on the service or client machines. For example, port 80 may be open through a firewall but other ports may be blocked.
Once you understand the addressability, protocol and port constraints on your service and its clients you can determine service and endpoint configuration. Use the table in the MSDN article “Working with NATS and Firewalls” at http://msdn.microsoft.com/en-us/library/ms731948.aspx to determine the best configuration for your scenario.