Break Sequence for Cisco devices
The change in computers that have moved away from serial ports and an actual “break” key on the keyboards makes it difficult for many people to get a Cisco device to drop to rommon mode on startup for recovery procedures. Now that laptops do not come with serial ports by standard and require a USB to serial adapter for network engineers to console into devices this has also caused issues with traditional break sequences.
The most common programs like HyperTerminal, Putty, and SecureCRT have a break sequence which is “Ctrl-Break”. The fact that many computers, laptops, and keyboards do not have a “break” key makes it very difficult to drop into rommon when accessing a Cisco device from the console port.
A rarely known trick to accessing the rommon mode of a Cisco device can be done without the use of the “break” key. It is more involved, but considering that most people will reload a switch/router numerous times in frustration to get the rommon prompt that this trick is actually a faster method.
Simulated Break Sequence for Cisco Devices:
The best method that I have found to work time after time is a simulated break sequence. This is a very straight forward method. Start with the router (or device – will reference router for simplicity) powered on. Access the routers console port with the standard console connection settings:
9600 baud rate
No parity
8 data bits
1 stop bit
No flow control
Once the prompt is up. Press enter to get some commands to the device even if it is to get the “login” to fail from a failed login attempt. Once done, change your console settings to the setup below.
1200 baud rate
No parity
8 data bits
1 stop bit
No flow control
Once the baud rate is changed then you will no longer see any new responses on your screen. Power cycle the router and immediately press and hold the space bar. Keep it pressed for about 10 – 20 seconds. Change your Baud rate back to 9600 and press enter. You should be in rommon mode. If not then repeat and hold the space bar down longer.
This process has worked for me on every device I have tried it on. Try it next time your stuck looking for the break key on your keyboard. For those that do have the Break key here are the known sequences below. IF those don’t work – try the above.
Good luck!
-Toby Arnett
