Have you tried going to http://[internal IP address] to see if that works? Of course if you are using a host header filter, you will not get very far this way. You could test thought by putting a local hosts entry on your workstation to point mysite.mydomain.com to the internal IP address. This way when you type http://mysite.mydomain.com in your browser it will translate to the internal IP and yet still present the proper header to the IIS server. If this works, then you will either have to make the hosts entry on all internal workstations, OR if you have separate DNS servers for External and Internal name resolution for the same zone, you could put another DNS entry in for the mysite.mydomain.com for the Internal IP address. If this is NOT the case, you could create another name for the site and use that in the header as well and put that name like myinternalsite.mydomain.com and put the Internal IP address in the DNS. You would have to tell IIS to allow this header as well or set up another site that points to the same location on the disk as the original site.