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Re: v6 subnet size for DSL & leased line customers
On Sat, 22 Dec 2007 12:53:52 -0800 "Christopher Morrow" <[email protected]> wrote: > > On Dec 22, 2007 12:23 PM, Ross Vandegrift <[email protected]> wrote: > > > > On Fri, Dec 21, 2007 at 01:33:15PM -0500, Deepak Jain wrote: > > > For example... Within one's own network (or subnet if you will) we can > > > absorb all the concepts of V4 today and have lots of space available. > > > For example... for the DMZ of a business... Why not give them 6 bits > > > (/122?) are we anticipating topology differences UPSTREAM from the > > > customers that can take advantage of subnet differences between /64 and > > > /56 ? > > > > I am confused on this point as well. IPv6 documents seem to assume > > that because auto-discovery on a LAN uses a /64, you always have to > > use a /64 global-scope subnet. I don't see any technical issues that > > require this though. ICMPv6 is capable of passing info on prefixes of > > any length - prefix length is a plain old 8bit field. > > > > Uhm, so sure the spec might be able to do something different than /64 > but most equipment I've used only does auto-conf if the prefix is a > /64 :( Somewhere along the path to ipng we got reverted to classful > addressing again :( > Not really. Classful IPv4 defined both an addressing structure *and* an agorithm to match destinations against the route table entries (i.e. classful forwarding won't match on a default route if the router knows at least one prefix within a classful network). IPv6 uses the longest match rule regardless of any addressing structure, and only uses structure for a few portions of the total IPv6 address space, for the operation of things like DHCPv6 and address autoconfiguration. A change in IPv6 addressing structure won't involve a change in the route table matching algorithm. Regards, Mark. -- "Sheep are slow and tasty, and therefore must remain constantly alert." - Bruce Schneier, "Beyond Fear"