The original setup for home security required that the customers router be placed after the home security router. Most routers would take an IP from the security router with no problems, some routers (apple airports) however wouldn't like playing second fiddle to the home security router. In that case a tech would try to use these settings to place the customers router in the DMZ of the security router thus bypassing and conflicts. But with an update early this year the home security router is now able to be placed behind the customers router making these settings kind of pointless. (if you have a technocolor screen)
Hope that was helpful