CIDR Explanation

Hi List,

     I am hoping that somebody might be able to help me out or point
me in the right direction. For the life of me I can't seem to get a
good grasp on CIDR notation. I see a lot of CIDR addresses every day,
but I have trouble figuring out the IP addresses on the fly. I am not
a complete newbie - I am quite familiar with the OSI model, TCP
handshakes, etc but this one area stumps me.

     I am particularly interested in it because I am going to be
setting up a snort box soon as well as an IP chains firewall to
segregate parts of the network. I would much rather use CIDR since it
can be much quicker at times, but I don't want to use it right now due
to my lack of knowledge which can cause security issues. Can anybody
offer advice/help? Thanks.

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