Shot in the dark here, but try going into SQL Server Config Manager (on the main server) and go to SQL Server Network Configuration -> Protocols for SQLEXPRESS (or whatever the instance name is). Right click on TCP/IP and go to Properties, and under the IP Addresses tab change the IP address under IP2 to the external IP of the “spoke” and the port for IPALL to 1433.
- NOTE: take note of the original settings, as this is not guaranteed to work.