The Cisco SR 520 Secure Router is now obsolete (past End-of-Life and End-of-Support status).
End-of-Sale Date: 2012-07-02
End-of-Support Date: 2017-07-31
Cisco's End-of-Life Policy
You can view a listing of available Routers offerings that best meet your specific needs
If you want support information for the Cisco SR 520 Secure Router documentation, it may be available through Cisco.com Search or in the Cisco Community