Update: I found a web page at MacShadows which lists default login credentials for many routers.
Here’s an easy way to determine the default password for many routers. You might need to know your router’s default password if you forget or don’t have a record of your router’s current password or if you end up resetting the router to its factory defaults. You can visit the Open Sez Me web site to locate your router and determine its default login information. I recently had to use this web site for a client whose router had been setup by a friend a few years ago. My client didn’t have any record of the password. I guessed that the friend hadn’t changed the password from its default. So, I used the Open Sez Me web site to locate the particular model of router and its default login information. Sure enough, it worked on my client’s router.