Definitive Guide to IPv6 adoption

Mark Andrews marka at isc.org
Mon Oct 18 20:32:05 CDT 2010


In message <35804BC3-9EFE-4CE4-B13A-F2E15C420EFA at americafree.tv>, Marshall Euba
nks writes:
> It makes a bigger difference if everyone starts using 6RD - to give out =
> a /48 effectively=20
> requires a  /16, and the number of /16s is by no means approximately =
> infinite.=20
> 
> Regards
> Marshall

Only if you deploy 6rd in a naive manner.  Encoding all of IPv4
into the IPv6 prefix you hand your customers in naive.

The best way is to just have a table that matches 6rd prefixes to
IPv4 blocks you have assigned.  This table only changes when you
add or remove a IPv4 assignments from RIRs.  You don't change
existing entries in the table.  The entries are static for the life
of the IPv4 allocation.

	<6rdPrefix1><6rdPefixLen1><IPv4Prefix1><IPv4PrefixLen1>
	<6rdPrefix2><6rdPefixLen2><IPv4Prefix2><IPv4PrefixLen2>
	<6rdPrefix3><6rdPefixLen3><IPv4Prefix3><IPv4PrefixLen3>

When you configure a IPv4 DHCP pool and associated router interface
you find the covering IPv4 prefix and plug in the values from the
table.

The next best way is to have a similar table but per covering IPv4/8
you have allocated.  This is very wasteful but not as having a 
IPv4PrefixLen of 0.

	<6rdPrefix1><6rdPefixLen><192.0.0.0><8>
	<6rdPrefix2><6rdPefixLen><202.0.0.0><8>

For the global naive case the table degenerates to a single row.

	<6rdPrefix><6rdPefixLen><0.0.0.0><0>

As a exercise the first table was ~20 entries for Comcast Cable and
the second table about ~10 entries if I did the lookup correctly
so we are not talking about a lot of prefixes and they don't change
very often.

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




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