Re: 16 year old bug

[der Mouse <mouse%Rodents-Montreal.ORG@localhost>]

> On the other hand, simple non-contig netmasks, with no ambiguity,
> certainly were permitted originally.  They work just fine.  They also
> offer essentially nothing over contig netmasks - they're just a
> permutation of the bits in the addresses.

I wouldn't say _nothing_.  See below.

> The one (the only) reason they were permitted, that I know of anyway,
> was that by allowing them we apparently let some (perhaps
> hypothetical) sites implement subnets without altering their existing
> IP numbering scheme.  I personally never saw such a site, and have no
> direct evidence one ever existed (or that anyone ever actually used
> non-contig netmasks for this reason) - but that was the argument
> anyway.

I have.  For a significant time (years) I was running my house LAN with
a netmask ending in (binary) 11011000, I think it was - a /29 expanded
by adding a second /29 from higher up.  (The memory is very fuzzy, but
255.255.255.216 looks right.)

The reason was exactly this: growing the space without renumbering when
the original space's pair had alreayd been allocated elsewhere.  Was it
necessary?  Not for most values of "necessary".  Was it useful?
Definitely.  Not visible outside its parent network, of course, but
that's true of most subnetting schemes, including CIDR ones, and it was
in live use for years.

>> I was actually at the pre-CIDR IETF meeting where it was discussed
>> whether to standardize the forwarding lookup for routes with
>> non-contiguous masks or disallow them altogether.

Out of scope.  A host's routing implementation is not visible from the
network; it is not a matter for the IETF to standardize.

If you want to forbid noncontiguous netmasks in wire protocols like BGP
or RIP or whatever, that is in scope, but also irrelevant to what
you're describing.

>> You are almost 20 years too late to influence that outcome.

Irrelevant.  Nobody off-network can tell whether I'm using
noncontiguous netmasks within my network, so nobody but my
co-administrators has standing to even comment on the question.

Of course, NetBSD may, if it wishes, desupport them.  It also may, if
it wishes, desupport netmask boundaries falling other than on octet
boundaries.  I would call the one a bug just as I would the other.

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