A typical home network router possesses two IP addresses, one for the internal home (LAN) and one for the external Internet (WAN) connection. How can you find the router IP addresses?

The internal, LAN-IP address is normally set to a default, private number. Linksys routers, for example, use 192.168.1.1 for their internal IP address. D-Link and Net gear routers typically use 192.168.0.1. Some US Robotics routers use 192.168.123.254, and some SMC routers use 192.168.2.1. No matter the brand of router, its default internal IP address should be provided in documentation. Administrators often have the option to change this IP address during router setup. In any case, however, the private LAN-IP address remains fixed once set. It can be viewed from the router's administrative console.

The external, WAN-IP address of the router is set when the router connects to the Internet service provider. This address can also be viewed on the router's administrative console.

Alternatively, the WAN-IP address can be found by visiting a Web-based IP address lookup service like http://checkip.dyndns.org/ from any computer on the home LAN.

Another way to identify the public IP addresses of routers, involves executing a ping or "trace route" command. From inside a home network, the (DOS) command "ping -r 1" will send a message through the home router that will cause its IP address to be displayed. For example, "ping -r 1 www.yahoo.com" should result in a message like the following displayed on the command prompt:
Reply from 66.94.230.43: bytes=32 time=294ms TTL=56
Route: 209.179.21.76

In this example, the IP address after "Route:" (209.179.21.76) corresponds to the router WAN address.