IP summary addressing cheatsheet.  See www.boson.com for updates.
    Check "ACRC-TCP-SUB.PDF" for detailed information.
	Copyright (c) 1999 by Boson Software
	Written by dave@boson.com

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Summarization Sanity Checker:
Any route summary can summarize 2, 4, 8, 16, 32, 64, 128, etc... (power of 2).
The first network in the range must be in the multiple of the number summarized routes.
Example 1/2: Summarize 32 routes; first network 0, 32, 64, 128, etc... (exact match).
Example 2/2: Summarize 6 routes; first summary is 4, next summary is 2. (takes 2)

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Shortcut example:
Given the question of 20 bits for summarization with TCP/IP,
  using a "/20" mask gives you 4 bits out of the 8 possible in that octet.

In binary, remember summaries are normal masks (not inverted like access-lists).
So, /20 bits = 11111111.11111111.11110000.0000, of which we only care about 11110000.

11110000 = 240 in decimal.  Here is the cool part.  Ready?  256 - 240 = 16.

Each valid summary will be a multiple of 16, starting at 16.


