Can't log into a router 2900 after downgrading IOS

[Daniel Vinyals Beltran]

Hello

last Friday I loaded a bew IOS file on a 2921 router. Today, remotely, I have reloaded it but now I can't load in to the router via Telnet, SSH or CCP. Obvioulsy, I have successfully established a Telnet session in order to send the reload command; it has reloaded and now it prompts for user/password but the ones I used before are no longer valid. Any help, please?

The older version was 151-4.M4 and the new one 151-3.T4

DAni                  

[jvodonnel]

I'm running into the same issue on a 1921.  From 15.2-4(M2) to 15.1-4(M2).

[Cesar Ortega]

Got the same problem when downgrading from 15.1(1)M4 to 15.1(1)M1. Any solution before trying password-recovery?

[jvodonnel]

Nope.  Password recovery was the solution.  I think it has to do with the type 4 vs type 5 hash issue.