Per recuperare la password bisogna procedere un 4 passi:
A) Cambiare in registro di configurazione
B) Resettare il router
C) Cambiare le password
D) Rimettere a posto il registro di configurazione

-----Preparazione--------
E' necessario collegarsi alla console del router.
L'interfaccia è una rs232 (dentro la confezione del router c'e' l'adattatore, altrimenti in fondo al manuale c'e' la piedinatura per farsi un cavetto)
Una volta connessi via seriale al router, bisogna lanciare un programma di comunicazioni (hiperterminal p.e.)

Configurazione della porta: 9600, nessuna parità, 8 bit, 1 bit stop, nessun controllo di flusso.

-------Passo A---------
A1)
dare il comando
show version
e annoratsi il valore del registro di configurazione (0x100 p.e.) nel caso del soho77 e' 0x2102

A2) spegnere il router e riaccenderlo
A3) aspettare qualche secondo
A4) lanciare un break (in hyperterminal premere Ctrl-Pausa)
il router dovrebbe rispondere
rommon 2>
A5) cambiare il registro di configurazione
rommon 2> confreg 0x142

-------Passo B---------
B1) resettare il router
rommon 2> reset

Il router riparte e mostrerà
--- System Configuration Dialog ---
-------Passo C---------
C1) rispondere sempre no fino a che non comparirà
Press RETURN to get started!
C2) premere return
C3) andare nella modalità privilegiata
nome_del_router> enable
C4) leggersi la configurazione
nome_del_router# show startup-config

Se il router è configurato con una password in chiaro la troverai scritta a fianco :
enable tua_password
se la password è crittata (enable secret) non è possibile leggerla ma solo codificarla:

C5)
nome_del_router# configure terminal

C6)
nome_del_router(config)# enable secret tua_nuova_password

C7)
nome_del_router(config)# exit

C8) salvare la configurazione
nome_del_router# copy running-config startup-config

----nota-----
La password che il router chiede quando si accede da telnet è nelle ultime righe della configurazione in un blocco del tipo:


line vty 0 4
password password_accesso_telnet
login


-------Passo D---------
D1)
nome_del_router# configure terminal

D2) rimettere a posto il registro di configurazione
nome_del_router(config)# config-reg valore_del_registro_annotato

D3) uscire
nome_del_router# exit

D4) resettare.........

e buona fortuna!


Giovanni

Dal sito Cisco :

http://www.cisco.com/en/US/products/hw/routers/ps2167/products_password_recovery09186a0080094c2a.shtml

Introduction

This document describes how to recover the enable password and the enable secret passwords. These passwords protect access to privileged EXEC and configuration modes. The enable password password can be recovered, but the enable secret password is encrypted and must be replaced with a new password. Use the procedure described in this document in order to replace the enable secret password.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

The information in this document is based on the Cisco SOHO 76, 77, 78, 91, 96, and 97 Routers.

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.

Related Products

Refer to Password Recovery Procedures for information on how to recover passwords for related products.

Conventions

Refer to Cisco Technical Tips Conventions for information on document conventions.

Step-by-Step Procedure

Follow these steps in order to recover your password:

  1. Attach a terminal or PC with terminal emulation to the console port of the router.

    Use these terminal settings:

    • 9600 baud rate

    • No parity

    • 8 data bits

    • 1 stop bit

    • No flow control

    Refer to these documents for information on how to cable and connect a terminal to the console port or the AUX port:

  2. If you can access the router, type show version at the prompt, and record the configuration register setting. See Example of Password Recovery Procedure in order to view the output of a show version command

    Note: The configuration register is usually set to 0x2102 or 0x102. If you can no longer access the router (because of a lost login or TACACS password), you can safely assume that your configuration register is set to 0x2102.

  3. Use the power switch in order to turn off the router, and then turn the router back on.

    Important Notes:

    • In order to simulate this step on a Cisco 6400, pull out and then plug in the Node Route Processor (NRP) or Node Switch Processor (NSP) card.

    • In order to simulate this step on a Cisco 6x00 with NI-2, pull out and then plug in the NI-2 card.

  4. Press Break on the terminal keyboard within 60 seconds of power up in order to put the router into ROMMON.

    If the break sequence does not work, refer to Standard Break Key Sequence Combinations During Password Recovery for other key combinations.

  5. Type confreg 0x2142 at the rommon 1> prompt in order to boot from Flash.

    This step bypasses the startup configuration where the passwords are stored.

  6. Type reset at the rommon 2> prompt.

    The router reboots, but ignores the saved configuration.

  7. Type no after each setup question, or press Ctrl-C in order to skip the initial setup procedure.

  8. Type enable at the Router> prompt.

    You are in enable mode and should see the Router# prompt.

  9. Type configure memory or copy startup-config running-config in order to copy the nonvolatile RAM (NVRAM) into memory.

    Important: Do not type copy running-config startup-config or write. These commands erase your startup configuration.

  10. Type show running-config.

    The show running-config command shows the configuration of the router. In this configuration, the shutdown command appears under all interfaces, which indicates all interfaces are currently shut down. In addition, the passwords (enable password, enable secret, vty, console passwords) are in either an encrypted or unencrypted format. You can reuse unencrypted passwords. You must change encrypted passwords to a new password.

  11. Type configure terminal.

    The hostname(config)# prompt appears.

  12. Type enable secret <password> in order to change the enable secret password. For example:

    hostname(config)#enable secret cisco

  13. Issue the no shutdown command on every interface that you use.

    If you issue a show ip interface brief command, every interface that you want to use should display up up.

  14. Type config-register <configuration_register_setting>. Where configuration_register_setting is either the value you recorded in step 2 or 0x2102 . For example:

    hostname(config)#config-register 0x2102

  15. Press Ctrl-z or end in order to leave the configuration mode.

    The hostname# prompt appears.

  16. Type write memory or copy running-config startup-config in order to commit the changes.

Example of Password Recovery Procedure

This section provides an example of the password recovery procedure. This example was created with a Cisco 2600 Series Router. Even if you do not use a Cisco 2600 Series Router, this output provides an example of what you should experience on your product.

Router>enable
Password:
Password:
Password:
% Bad secrets

Router>show version
Cisco Internetwork Operating System Software
IOS (tm) C2600 Software (C2600-IS-M), Version 12.0(7)T, RELEASE SOFTWARE (fc2)
Copyright (c) 1986-1999 by cisco Systems, Inc.
Compiled Tue 07-Dec-99 02:21 by phanguye
Image text-base: 0x80008088, data-base: 0x80C524F8

ROM: System Bootstrap, Version 11.3(2)XA4, RELEASE SOFTWARE (fc1)

Router uptime is 3 minutes
System returned to ROM by abort at PC 0x802D0B60
System image file is "flash:c2600-is-mz.120-7.T"

cisco 2611 (MPC860) processor (revision 0x202) with 26624K/6144K bytes of memory.
Processor board ID JAB031202NK (3878188963)
M860 processor: part number 0, mask 49
Bridging software.
X.25 software, Version 3.0.0.
Basic Rate ISDN software, Version 1.1.
2 Ethernet/IEEE 802.3 interface(s)
2 Serial(sync/async) network interface(s)
1 ISDN Basic Rate interface(s)
32K bytes of non-volatile configuration memory.
8192K bytes of processor board System flash partition 1 (Read/Write)
8192K bytes of processor board System flash partition 2 (Read/Write)

Configuration register is 0x2102

Router>



!--- The router was just powercycled, and during bootup a
!--- break sequence was sent to the router.


!

*** System received an abort due to Break Key ***

signal= 0x3, code= 0x500, context= 0x813ac158
PC = 0x802d0b60, Vector = 0x500, SP = 0x80006030
rommon 1 > confreg 0x2142

You must reset or power cycle for new config to take effect

rommon 2 > reset

System Bootstrap, Version 11.3(2)XA4, RELEASE SOFTWARE (fc1)
Copyright (c) 1999 by cisco Systems, Inc.
TAC:Home:SW:IOS:Specials for info
C2600 platform with 32768 Kbytes of main memory


program load complete, entry point: 0x80008000, size: 0x6fdb4c

Self decompressing the image : ###############################
##############################################################
##############################################################
##############################################################
############################### [OK]


 Restricted Rights Legend

Use, duplication, or disclosure by the Government is
subject to restrictions as set forth in subparagraph
(c) of the Commercial Computer Software - Restricted
Rights clause at FAR sec. 52.227-19 and subparagraph
(c) (1) (ii) of the Rights in Technical Data and Computer
Software clause at DFARS sec. 252.227-7013.

 cisco Systems, Inc.
 170 West Tasman Drive
 San Jose, California 95134-1706

Cisco Internetwork Operating System Software
IOS (tm) C2600 Software (C2600-IS-M), Version 12.0(7)T, RELEASE SOFTWARE (fc2)
Copyright (c) 1986-1999 by cisco Systems, Inc.
Compiled Tue 07-Dec-99 02:21 by phanguye
Image text-base: 0x80008088, data-base: 0x80C524F8

cisco 2611 (MPC860) processor (revision 0x202) with 26624K/6144K bytes of memory.
Processor board ID JAB031202NK (3878188963)
M860 processor: part number 0, mask 49
Bridging software.
X.25 software, Version 3.0.0.
Basic Rate ISDN software, Version 1.1.
2 Ethernet/IEEE 802.3 interface(s)
2 Serial(sync/async) network interface(s)
1 ISDN Basic Rate interface(s)
32K bytes of non-volatile configuration memory.
8192K bytes of processor board System flash partition 1 (Read/Write)
8192K bytes of processor board System flash partition 2 (Read/Write)


 --- System Configuration Dialog ---

Would you like to enter the initial configuration dialog? [yes/no]: n

Press RETURN to get started!

00:00:19: %LINK-3-UPDOWN: Interface BRI0/0, changed state to up
00:00:19: %LINK-3-UPDOWN: Interface Ethernet0/0, changed state to up
00:00:19: %LINK-3-UPDOWN: Interface Ethernet0/1, changed state to up
00:00:19: %LINK-3-UPDOWN: Interface Serial0/0, changed state to down
00:00:19: %LINK-3-UPDOWN: Interface Serial0/1, changed state to down
00:00:20: %LINEPROTO-5-UPDOWN: Line protocol on Interface BRI0/0, 
changed state to down
00:00:20: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0,
 changed state to up
Router>
00:00:20: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/1, 
changed state to up
00:00:20: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, 
changed state to down
00:00:20: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/1, 
changed state to down
00:00:50: %SYS-5-RESTART: System restarted --
Cisco Internetwork Operating System Software
IOS (tm) C2600 Software (C2600-IS-M), Version 12.0(7)T, RELEASE SOFTWARE (fc2)
Copyright (c) 1986-1999 by cisco Systems, Inc.
Compiled Tue 07-Dec-99 02:21 by phanguye
00:00:50: %LINK-5-CHANGED: Interface BRI0/0, 
changed state to administratively down
00:00:52: %LINK-5-CHANGED: Interface Ethernet0/0, 
changed state to administratively down
00:00:52: %LINK-5-CHANGED: Interface Serial0/0, 
changed state to administratively down
00:00:52: %LINK-5-CHANGED: Interface Ethernet0/1, 
changed state to administratively down
00:00:52: %LINK-5-CHANGED: Interface Serial0/1, 
changed state to administratively down
00:00:53: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0, 
changed state to down
00:00:53: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/1, 
changed state to down
Router>
Router>enable
Router#copy startup-config running-config
Destination filename [running-config]?
1324 bytes copied in 2.35 secs (662 bytes/sec)
Router#
00:01:24: %LINEPROTO-5-UPDOWN: Line protocol on Interface BRI0/0:1, 
changed state to down
00:01:24: %LINEPROTO-5-UPDOWN: Line protocol on Interface BRI0/0:2, 
changed state to down
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#enable secret < password >
Router(config)#^Z
00:01:54: %SYS-5-CONFIG_I: Configured from console by console
Router#show ip interface brief

Interface   IP-Address        OK?  Method     Status                   Protocol
Ethernet0/0 10.200.40.37      YES  TFTP       administratively down    down
Serial0/0   unassigned        YES  TFTP       administratively down    down
BRI0/0      193.251.121.157   YES  unset      administratively down    down
BRI0/0:1    unassigned        YES  unset      administratively down    down
BRI0/0:2    unassigned        YES  unset      administratively down    down
Ethernet0/1 unassigned        YES  TFTP       administratively down    down
Serial0/1   unassigned        YES  TFTP       administratively down    down
Loopback0   193.251.121.157   YES  TFTP       up                       up
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#interface Ethernet0/0
Router(config-if)#no shutdown
Router(config-if)#
00:02:14: %LINK-3-UPDOWN: Interface Ethernet0/0, changed state to up
00:02:15: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0, 
changed state to up
Router(config-if)#interface BRI0/0
Router(config-if)#no shutdown
Router(config-if)#
00:02:26: %LINK-3-UPDOWN: Interface BRI0/0:1, changed state to down
00:02:26: %LINK-3-UPDOWN: Interface BRI0/0:2, changed state to down
00:02:26: %LINK-3-UPDOWN: Interface BRI0/0, changed state to up
00:02:115964116991: %ISDN-6-LAYER2UP: Layer 2 for Interface BR0/0, 
TEI 68 changed to up
Router(config-if)#^Z
Router#
00:02:35: %SYS-5-CONFIG_I: Configured from console by console
Router#copy running-config startup-config
Destination filename [startup-config]?
Building configuration...
[OK]
Router#show version
Cisco Internetwork Operating System Software
IOS (tm) C2600 Software (C2600-IS-M), Version 12.0(7)T, RELEASE SOFTWARE (fc2)
Copyright (c) 1986-1999 by cisco Systems, Inc.
Compiled Tue 07-Dec-99 02:21 by phanguye
Image text-base: 0x80008088, data-base: 0x80C524F8

ROM: System Bootstrap, Version 11.3(2)XA4, RELEASE SOFTWARE (fc1)

Router uptime is 3 minutes
System returned to ROM by abort at PC 0x802D0B60
System image file is "flash:c2600-is-mz.120-7.T"

cisco 2611 (MPC860) processor (revision 0x202) 
with 26624K/6144K bytes of memory.
Processor board ID JAB031202NK (3878188963)
M860 processor: part number 0, mask 49
Bridging software.
X.25 software, Version 3.0.0.
Basic Rate ISDN software, Version 1.1.
2 Ethernet/IEEE 802.3 interface(s)
2 Serial(sync/async) network interface(s)
1 ISDN Basic Rate interface(s)
32K bytes of non-volatile configuration memory.
8192K bytes of processor board System flash partition 1 (Read/Write)
8192K bytes of processor board System flash partition 2 (Read/Write)

Configuration register is 0x2142

Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#config-register 0x2102
Router(config)#^Z
00:03:20: %SYS-5-CONFIG_I: Configured from console by console

Router#show version
Cisco Internetwork Operating System Software
IOS (tm) C2600 Software (C2600-IS-M), Version 12.0(7)T, RELEASE SOFTWARE (fc2)
Copyright (c) 1986-1999 by cisco Systems, Inc.
Compiled Tue 07-Dec-99 02:21 by phanguye
Image text-base: 0x80008088, data-base: 0x80C524F8

ROM: System Bootstrap, Version 11.3(2)XA4, RELEASE SOFTWARE (fc1)

Router uptime is 3 minutes
System returned to ROM by abort at PC 0x802D0B60
System image file is "flash:c2600-is-mz.120-7.T"

cisco 2611 (MPC860) processor (revision 0x202) 
with 26624K/6144K bytes of memory.
Processor board ID JAB031202NK (3878188963)
M860 processor: part number 0, mask 49
Bridging software.
X.25 software, Version 3.0.0.
Basic Rate ISDN software, Version 1.1.

2 Ethernet/IEEE 802.3 interface(s)
2 Serial(sync/async) network interface(s)
1 ISDN Basic Rate interface(s)
32K bytes of non-volatile configuration memory.
8192K bytes of processor board System flash partition 1 (Read/Write)
8192K bytes of processor board System flash partition 2 (Read/Write)

Configuration register is 0x2142 (will be 0x2102 at next reload)

Router#