We have a web server (IIS) and a database server (MS SQL 2005) separated by an application proxy / firewall. We want to keep the number of open ports between the two machines at a minimum. Obviously port 1433 (or equivalent) is needed, however, we also need to support MSDTC transactions. The MS advice here suggests port 135 and a range of other ports.
However, there is no guidance regarding the number of ports to keep open. Is one enough? Do I need ten? What determines the number of ports we need open.
Any pointers appreciated!