From: Matt Bentley (mattdbentley@gmail.com)
Date: Fri Mar 14 2008 - 12:23:13 ARST
Hi Team:
I know my knowledge here is a little lacking, but I really need some help.
I just cannot seem
to get a handle of summarizing routes. I have a few questions I would be
VERY grateful to have
answered.
When I am told to summarize routes overlapping as little address space as
possible, sometimes I see answers where there are two lines. Why are there
two lines. How do I know I shouldn't just do one line? Is there something
about major network boundaries that I don't know?
Also, I have read lots of documents on how to do binary xor/and, but it just
doesn't make sense when I do it.
For example:
10.12.13.11
10.12.14.201
I know the first two octets are the same, so I don't have to worry about
them. So, I take the binary of the third and fourth octets.
00001101 00001011
00001110 11001001
------------------
00001101 00001001 = AND (Network portion) = 13.9
00000011 11001010 = XOR (Mask Portion) = 2.204
So, is the summary 10.12.13.9 0.0.2.204 ????
What am I doing wrong.
How do I know that the mask should be zeros instead of 255's to start out
with? Something to do with access-lists?
Could someone show me an example and the theory behind knowing when you need
two statements
to summarize a certain address range as opposed to one? Is it a hard and
fast rule, or just a best practice sort of thing?
Thanks very much in advance.
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