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Re: IPV6 Training Books
From: Mark Andrews <marka () isc org>
Date: Tue, 05 Apr 2011 10:59:31 +1000


In message <690D7D20D2507C44BA8066926B2009890867FA () ES1002 ic-sa com>, Michael R
uiz writes:
Hello All,

                I am looking for some good reading material to get a better=
 understanding of IPV6.  I know how to convert HEX into decimal format.  Wh=
at I am looking for is how to under the CIDR notation and break them out in=
to subnets.   Thank you in advance.

If you think in hex its straight forward to do CIDR in IPv6.  There
are only three groupings on a non nibble boundaries.  You also
display the entire 128 bits with the least significant bits set to
zero.  The :: notation is used to shorten the displayed address.

e.g for a /57, /58 and /59 with leading bits of 2001:23bc:fe8d:b200::/56
you would have.

/57     {0,1,2,3,4,5,6,7} {8,9,a,b,c,d,e,f}
        2001:23bc:fe8d:b200::/57
        2001:23bc:fe8d:b280::/57
/58     {0,1,2,3} {4,5,6,7} {8,9,a,b} {c,d,e,f}
        2001:23bc:fe8d:b200::/58
        2001:23bc:fe8d:b240::/58
        2001:23bc:fe8d:b280::/58
        2001:23bc:fe8d:b2c0::/58
/59     {0,1} {2,3} {4,5} {6,7} {8,9} {a,b} {c,d} {e,f}
        2001:23bc:fe8d:b200::/59
        2001:23bc:fe8d:b220::/59
        2001:23bc:fe8d:b240::/59
        2001:23bc:fe8d:b260::/59
        2001:23bc:fe8d:b280::/59
        2001:23bc:fe8d:b2a0::/59
        2001:23bc:fe8d:b2c0::/59
        2001:23bc:fe8d:b2e0::/59

Note the last nibble before the :: is 0 and is there so that the
final bits are all zeros.  The following all represent the same
cidr block.

        2001:23bc:fe8d:b2e0::/59
        2001:23bc:fe8d:b2e0:0000:0000:0000:0000/59
        2001:23bc:fe8d:b2e0:0:0:0:0/59

Normally you just assign /64 subnets and delegate address blocks
on nibble boundaries to end customers, e.g. /48, /52, /56 or /60.
This means that end customers don't need do deal with cidr block
if they don't want to.  They can just route individual /64.

MAR.

-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka () isc org


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