The default username and password is the same as the 5200: [admin/admin]
What is the username and password for the 5200?
Hint: If your ISP has changed it, then only a reset will remove it on the Web Interface. Reset instructions are located only in the User Guide.
Note: Don't confuse the Web Interface Login Username/Password with a ISP Customized Admin Username/Password for the configuration since that is not the same. If your ISP has set that up in your Modem/Router then you must request the Username/Password from them as a reset doesn't change that.