RE: IPV6 Address Summarization

From: Joseph Brunner (joe@affirmedsystems.com)
Date: Thu Aug 30 2007 - 16:47:50 ART


The first 48 bits wont change, agreed?
2001:141:1
2001:141:1

Lets look at the 16 bits of the 128 where have a different value...

12 in hex is shorted from 0012
25 in hex is shorted from 0025

Each XX equals 8 bits

So

00000000
00000000

That means we already have a /56 up to midway through the 4th 16 bit
block...

Now convert each nibble to binary and pad up to /64...

      1 2
 00000110

     2 5
 00010101

00000000000 (11 zero's of similarity in the 4th 16th bit block)

11 + 48 = 59

You are correct it's a /59

Who told you other wise?

-Joe

-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Sadiq Yakasai
Sent: Thursday, August 30, 2007 2:56 PM
To: Cisco certification
Subject: IPV6 Address Summarization

Hi Guys,

Please could someone help out a guy here:

I need to summarize these two IPV6 addresses:
2001:141:1:12::/64
2001:141:1:25::/64

I have done it many times over, and what I find to be the summarized address
is:
2001:141:1::/59

However, an excercise I am doing here says is
2001:141:1::/58

Please can someone confirm if I am right or wrong here?

Thanks!!

Sadiq



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