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The default config register of an IOS device is 0x2102. The table here clearly states that 0x0100 signifies "Ignore Break," and that the default config register employs these options:

Ignores break
Boots into ROM if initial boot fails
9600 console baud rate default value for most platforms

In practice, and per Cisco's documentation, you are able to break the startup of a device with the default config register (mainly for bypassing/resetting passwords), so what gives?

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up vote 2 down vote accepted

Break can always be sent during the first 60 seconds of the bootstrap process, regardless of the configuration setting.

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What is the point of the flag then? I can't find this documented anywhere, but breaking obviously works, so this must be the reason. – Jan 6 '13 at 16:10
The point of the flag is to allow you to disable break during normal operation of the router. – David Schwartz Jan 7 '13 at 0:48

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