C# – A WCF service behind a firewall generates a wrong wsdl URI

I developed a WCF service and i have published it with IIS. All goes well inside the local network but when the service is accessed by an external client from the internet, redirected by a firewall, the service generates a local wsdl uri that cannot be solve by the client.

Something like this:

• URI needed: http://external_url/service.svc?wsdl
• URI created: http://internal_url/service.svc?wsdl

I would like to continue using the automatic generation of the wsdl file without indicating an external path. I also have prove manipulating the ServiceBehavior attribute into the service class but the problem persists.

How can I do it?