Finding Out External IP of a Router

The DSL and Cable routers have two IP addresses, one is visible on internal network that PCs on home network see and second is visible on external network that Internet sees. For various reasons one may need to find external IP address of the router. There are few ways to do that, but simplest is to goto the this link (http://checkip.dyndns.org/) from a computer inside your home network. It prints the external IP address of the router.