[c-nsp] Access-list Question

[Scott Granados]

Well can't we don't care bit ourselves around to masking or something
consistent?  It is confusing at times although it's interesting to know
that's the origin. 

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Tony Li
Sent: Tuesday, May 15, 2007 11:05 PM
To: Brian McMahon
Cc: cisco-nsp
Subject: Re: [c-nsp] Access-list Question


On May 15, 2007, at 10:00 PM, Brian McMahon wrote:

> My personal theory (SWAG) is that, long ago in the Elder Days of
> single-digit IOS version numbers, some clever programmer figured out
> a way to save a couple of processor cycles per ACL by coding the
> bitmask this way around -- an efficiency gain that has been easily
> swamped over the years by the confusion it's created, but that is now
> WAY TOO LATE to fix.


Close.  You have the timing right.  The modeling was based on "don't  
care bits" as commonly found in hardware design.  Netmasks hadn't  
really caught on as of then.

Tony


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