ISP customer assignments
mysidia at gmail.com
Wed Oct 7 00:02:34 UTC 2009
>> unimaginably huge *classless* network. Yet, 2 hours into day one, a
>> classful boundary has already been woven into it's DNA. Saying it's
No bit patterns in a V6 address indicate total size of a network. v6
doesn't bring classful addressing back or get rid of CIDR..
v6 dispenses with something much older: common use of VLSM on the
local LAN and sizing subnets based on the number of hosts.
Instead a form of FLSM is recommended, a fixed standard subnet size of /64
that essentially all IPv6 networks use for the subnets that have hosts on them.
This restores consistency to LAN addressing.
In V4 there is a valid reason for choosing VLSM and sizing every
subnet: IP addresses are scarce. V6 removes that scarcity problem.
No more unanticipated growth necessitating an addressing re-design,
or at least error-prone adjustment of netmasks on all hosts.
No more hodgepodge of different netmask settings for different sized LANs.
No more LAN address ranges starting or ending with a different
trailing string of digits than other LANs.
/64 is the standard.
V6 leaves the operator able to pick something different, but in most cases it
would be a very poor design practice, and ISPs should think long and
hard before ignoring the standard and trying to issue a customer
subnet a /128, instead of /48 or /56.
However... none of the network protocol documents were ever able to
prevent determined people from coming up with bad designs, or
ignoring recommendations due to politics or preconceived notion(s);
don't hold your breath on that one...
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