Contents

Introduction

Prerequisites

Requirements

Components Used

Conventions

Background Information

Standard Break Key Combinations

How to Troubleshoot Issues

How to Simulate a Break Key Sequence

Related Information

Introduction

This document describes the standard break key sequence combinations for the operating systems and how to fix any issues.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

This document is not restricted to specific software and hardware versions.

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, ensure that you understand the potential impact of any command.

Conventions

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

Background Information

The Electronic Industries Association RS-232 logic level uses +3 to +25 volts to signify a Space (Logic 0) and -3 to -25 volts for a Mark (logic 1). A break signal is when the data line remains in the space condition for a specified duration, usually 100 ms to ½ second. All characters begin with a start bit and end with a stop bit (and also a parity bit or two). The level condition of the start and stop bits is always opposite. So, no character combination can look like the break signal. A break signal enables you to access a ROM Monitor on Cisco IOS® devices when a password recovery is necessary.

Standard Break Key Combinations

Software

Platform

Operating System

Try This

Hyperterminal

IBM Compatible

Windows XP

Ctrl-Break

Hyperterminal

IBM Compatible

Windows 2000

Ctrl-Break

Hyperterminal

IBM Compatible

Windows 98

Ctrl-Break

Hyperterminal (version 595160)

IBM Compatible

Windows 95

Ctrl-F6-Break

Kermit

Sun Workstation

UNIX

Ctrl-\l

Ctrl-\b

MicroPhone Pro

IBM Compatible

Windows

Ctrl-Break

Minicom

IBM Compatible

Linux

Ctrl-a f

ProComm Plus

IBM Compatible

DOS or Windows

Alt-b

SecureCRT

IBM Compatible

Windows

Ctrl-Break

Telix

IBM Compatible

DOS

Ctrl-End

Telnet

N/A

N/A

Ctrl-], then type send brk

Telnet to Cisco

IBM Compatible

N/A

Ctrl-]

Teraterm

IBM Compatible

Windows

Alt-b

Terminal

IBM Compatible

Windows

Break

Ctrl-Break

Tip

Sun Workstation

UNIX

Ctrl-], then Break or Ctrl-c

~#

VT 100 Emulation

Data General

N/A

F16

Windows NT

IBM Compatible

Windows

Break-F5

Shift-F5

Shift-6 Shift-4 Shift-b (^$B)

Z-TERMINAL

Mac

Apple

Command-b

N/A

Break-Out Box

N/A

Connect pin 2 (X-mit) to +V for half a second

Cisco to aux port

N/A

Control-Shft-6, then b

IBM Compatible

N/A

Ctrl-Break

How to Troubleshoot Issues

- Problems that you encounter during password recovery often occur because you are not sure about what the break key sequence is for the (non-Cisco) software you use. For software not listed in the table, and for additional information, refer to the documentation of the individual software packages.

- The auxiliary (AUX) port is not active during the boot sequence of a router. Therefore, it is no use if you send a break through the AUX port. You need to have connection to the console port, and have these settings:

9600 baud rate

No parity

8 data bits

1 stop bit

No flow control

- Some versions of Windows NT have hyperterminal software that cannot send the correct break key signal. Refer toHilgraeve Hyperterminal Emulation Program for more information and for an upgrade of the hyperterminal software.

- In some cases, the break sequence can be transmitted improperly when a USB/Serial converter cable is used. In such cases, use a keyboard with a different connector port (for example, a PS/2).

How to Simulate a Break Key Sequence

Break key sequence simulation is useful if your terminal emulator does not support the break key, or if a bug does not allow your terminal emulator to send the correct signal.

Note: The hyperterminal under Windows NT had this behavior in the past.

Complete these steps to simulate a break key sequence:

1. Connect to the router with these terminal settings:

1200 baud rate

No parity

8 data bits

1 stop bit

No flow control

You no longer see any output on your screen, and this is normal.

2. Power cycle (switch off and then on) the router and press the SPACEBAR for 10-15 seconds in order to generate a signal similar to the break sequence.

3. Disconnect your terminal, and reconnect with a 9600 baud rate. You enter the ROM Monitor mode.

If all these methods fail to properly send a break, retry the procedures from a different terminal or PC platform.

Related Information

- Cisco Technical Support & Downloads