I remember from my old dialup days there were some diallers or whatever that would launch certain software upon connection, for example the browser.
If there's a specific program being used to activate the connection, log in via PPPoE or whatever there may be settings in there to allow you to turn off it automaticall yopening a browser.
If there's a specific program being used to activate the connection, log in via PPPoE or whatever there may be settings in there to allow you to turn off it automaticall yopening a browser.