there could be many possibility such as router stuck in boot process, hangs in rommon state, lost both the nable and secret password, or password disbled, or someone leaving the company and not leaving the correct passwords behind etc...
but we cannot recover a device if the No Service Password-Recovery feature was enabled using the
no service password-recovery strict command, pls refer the below docs for more on the same.
http://www.cisco.com/c/en/us/td/docs/routers/access/4400/feature/guide/isr4451nspr.html
http://www.cisco.com/c/en/us/support/docs/routers/2600-series-multiservice-platforms/22188-pswdrec-2600.html
-Venkatesh
Do rate helpful post
