Write an article based on this summary:

Check your physical router for the IP address. Click the Apple menu and select "System Preferences. Click the "Network" button. Select your active connection in the left frame. Click the "Advanced" button. Click the "TCP/IP" tab and look for the "Router" entry.
You'll access your router's configuration page by entering its IP address into a web browser on your computer. Most routers have the IP address printed on a sticker on the bottom. If your router doesn't have this sticker, or you can't physically access the router, follow the instructions in this method. If you are using an Apple AirPort router, see the Updating an AirPort Router section below instead. " This will open a new System Preferences window. This will display all of your network connections. It will have a green indicator next to it, and will say "Connected" underneath. Make sure you're connected to the router's network. This will open a new window. This is the IP address for your router.