Why must a router be configured?

Answer 1

Routers have to be configured because computers are by definition "stupid". What I mean by this is that computers do only what people program or tell them what to do. A router is programmed to communicate and transfer data between computers. If you don't tell or configure the router what devices to communicate with, it will draw a big question mark and do nothing. Routers have come a long way in the past several years, making it fairly easy to set them up, and most companies (like linksys) will help you set up your router if you are unsure of how to do so. Even so, they still have to be configured so they can do what they are designed to do, ROUTE!

Answer 2

I will reply for the case of a Cisco router, which I know best. The default configuration of a Cisco router is that all interfaces (ports) are disabled. Pressumably this is for security concerns (i.e., don't enable anything that you might not use). Second, each interface needs an IP address. A default IP address wouldn't make sense here, since the IP address of the router has to be in the same subnet as the other hosts connected to that subnet. Third, the router may require additional configuration, depending on the technology options required. A simple case is that even if you connect only two routers, either a routing protocol or static routes have to be programmed, because otherwise, each router won't know about the existence of networks which are not directly connected (the networks to which the other router is connected).