Ascend Archive
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Re: (ASCEND) IP Addresses needed for 4048 (fwd)



On Wed, Apr 01, 1998 at 01:50:11PM -0500, Joe Pautler wrote:
> MegaZone wrote:
> ]
> ]Actually no, you don't lose the IPs when using VLSM.
> 
> Sure you do... you lose the broadcast address for each subnet.
> If you have a class B (/16), you lose address ???.???.255.255/16
> as a broadcast address.  If you break that class B into
> 255 class C's (/24), you lose a broadcast address for each subnet...
> in other words, 255 of them.  The same is true for VLSM's.

By no means ;)

The only case where you indeed lose addresses is when you apply them to
a shared medium multiple access point-to-multipoint broadcast network,
like Ethernet, FDDI and so on. You _never_ lose these addresses from
a routing standpoint, because for routing they are in no way special
addresses (this is why a directed broadcast works). If you don't apply
a /x to a broadcast network there is no reason to waste the all zeros
and all ones address because the only reason why they are reserved (as
a placeholder for a broadcast destination and, in the old days before
VLSM/CIDR, to name a classical network) has vanished (no broadcast concept
and no classful stuff any longer). There are no technical problems with
routing lets say 192.168.1.32/27 to a Max and defining the pool there
as 194.168.1.32 + 32 - if the Max refrains from doing it it does so
without a real reason.

-- 

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