[34508] in North American Network Operators' Group
Re: Cisco Flash help needed
daemon@ATHENA.MIT.EDU (Simon Lockhart)
Fri Feb 9 09:26:44 2001
To: cisco-nsp@puck.nether.net, nanog@merit.edu
In-Reply-To: Your message of "Thu, 08 Feb 2001 19:12:48 GMT."
<25478.981659568@sunf25>
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Date: Fri, 09 Feb 2001 14:24:22 +0000
Message-Id: <6728.981728662@sunf25>
From: Simon Lockhart <simonl@rd.bbc.co.uk>
Errors-To: owner-nanog-outgoing@merit.edu
>I've come across 2 CRCs so far - a 32 bit one used on the Class A cards,
>and a 16 bit one used on the Class B cards. I've tried a standard crc32
>routine (stolen from ssh), but it doesn't match the CRC reported by the
>router. Is there anyone good at understanding CRC routines who can help me
>reverse-engineer the cisco CRC, or perhaps does someone have some inside
>information they would like to share?
After some suggestions from various people, I tried uploading a few test
files onto a Cisco and seeing how the CRCs worked out. It turns out it's
not a true CRC at all, but rather a variation on the TCP checksum
algorithm.
>Please don't ask me for the code yet! I'll let the list know when it's
>available...
v0.1 of the code is now available (read only at the moment):
ftp://ftp.bbc.co.uk/pub/ciscoflash/
Enjoy,
Simon
--
Simon Lockhart | Tel: +44 (0)1737 839676
Internet Engineering Manager | Fax: +44 (0)1737 839516
BBC Internet Services | Email: Simon.Lockhart@bbc.co.uk
Kingswood Warren,Tadworth,Surrey,UK | URL: http://support.bbc.co.uk/
