It happens to lost the password for Alcatel Omniswitches 6250/6450 series.
To recover the password you have to press “s” key at booting that will boot your switch into some kernel location where you can delete user table with passwords included (it means you will reset/delete current password list)

WARNING: Stopping in miniboot as directed by boot flags…
 [Miniboot]->cd "network"
 value = 0 = 0x0
 [Miniboot]->ls
 .
 ..
 userTable5
 lockoutSetting
 policy.cfg
 ssh_host_dsa_key
 ssh_host_dsa_key.pub
 value = 0 = 0x0
 [Miniboot]->xdelete "userTable5"
 value = 0 = 0x0
 [Miniboot]->reboot
 mgi0 Interface Down
 mgi0 Interface Stopped
 WARNING: "sysResetHardwareFlag" flag is SET, forcing CMM board reset.