Subject: Re: IPv6 Addr/Prefix clarification

From: Keith Moore <[email-masked]>
Date: Wed, 23 Jan 2002 12:33:03 -0500

> I have to disagree with Keith here. If a site wants to subnet,
> they get a /48 and use the 16 SLA bits to subnet, that is what
> they have been designed for.

depends on what you mean by 'site', I suppose.  Even if RFC 3177 is 
followed, I would not want the network to presume that a /64 net
(such as might be assigned to a mobile network) should never be
subnetted.  there are good reasons to occasionally subnet a mobile
network.  and if we are not careful about how we allocate the 
top 64 bits we might need to allow subnetting of the lower 64 bits.

In general, code and hardware should not presume much about the 
structure of addresses.

Keith
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From: "Michel Py" <[email-masked]>
Date: Wed, 23 Jan 2002 08:13:44 -0800

>> Irina Dayal wrote:
> 1) Is it safe to assume that all IPv6 prefixes will be between
>> 16 and 64 bits long?

> Keith Moore wrote:
> no.  because nothing requires a site to use the lower 64 bits
> as an interface ID - a site is free to subnet that space if
> it wishes.

Michel.