The Is Active setting on Web Servers in ConfigDB is used by our meta data system to synchronize meta data.
When there are changes in meta data, like changing business object definitions in the Admin UI, the system notifies all the web servers of the changes.
There might be issues with synchronization when changes are made on the Application Server inside the firewall, and there is no direct access to the Web Server (outside the firewall) from the Application Server. Another potential issue is that the Web Server cannot be accessed from the Application Server using SSL.
Please also see KB 12292 for other troubleshooting steps.
In both of the above cases, you can set the "Is Active" flag to false on the Web Servers in ConfigDB.
You can still synchronize the changes made to the metadata by restarting IIS on the Web Servers that are not active, which will retrieve the new metadata from the database.