This module manages ISP connections and shows the current ISP connections state. Many companies use 24/7 access to Internet but even if you don't there is some task manager to enable/disable ISP connection at specified time. Sometimes all connections get disconnected and using this module you can connect to ISP again with web gui.
If you have several ISP connections at the same time then you need to define what is default. Otherwise the first started is the default one.
Pic.: The current state of available interfaces of the proxy server. ppp3 is the default gateway connected to ByFly ISP, ppp4 is connected to Atlant ISP.