How does a 'router setup page' work?
 

I'm trying to learn more about web developement and I have a simple question which google won't tell me the answer to (probably cos I don't know how to describe the question concisely).

I would like to know how a 'router setup webpage' can change the settings in the router.
This is my guess:
1) The router has a 'web server' running in it.
2) The router has another server running in it listerning for requests to change the setup (call it SetupServer).
3) A browser running on a pc on the network requests an html document (web page) from the router's webserver.
4) The web page has an ActiveX control in it which communicates directly to the SetupServer on the router.

2 and 4 sound all wrong to me. If anyone could tell me how it actually works I'd be grateful!!

Why would use need a separate setup server, or an ActiveX control? All you need is a webserver linked up to some configuration files (or database, or some other system for storing configuration) that controls the router's settings.

For instance, if your router runs an embedded form of Linux, then the server on the router might be designed to change certain network config files when a user clicks a button on the setup website.

Thanks Arevos, it all makes sense now!! I knew my answer was stupidly wrong, lol lol :)