Ascend Archive
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Re: (ASCEND) Low bit/high bit subnets
On Sat, Aug 09, 1997 at 11:36:23AM -0500, John Coy wrote:
> I was wondering if the Ascend products will properly
> route 'illegal' subnets such as the 0-bit and the high-bit
> subnets. For example, if I have /27 network, can I use:
Since the advent of VLSM (variable length subnet masks) this limitation
is completely obsolete in intra-domain routing (was this '89 ?). Since '94
we're also doing CIDR. This limitation is therefore dead for a number of
years, and software still requiring it is broken. For gods sake, Ascends
don't have these kinds of limitations. They had a problem with "super-
netting" routes for a while (i.e. using a shorter prefix length than the
classful implicit mask would be), but that's off as well.
> 208.133.27.0/27 (for IP's 208.133.27.1 - 208.133.27.31)
>
> or
>
> 208.133.27.224/27 (for IP's 208.133.27.225 - 208.133.27.254)?
Clearly this works. Actually, ISPs _need_ to route such nets to their
customers whith limited address space needs (so-called VSEs -Very Small
Enterprises). And if you place a request for address space f.i. at the
RIPE, you _have to_ use these nets, too.
> On my network, my Ascend routes propagate back to a Cisco router and
> I am certain there is a way to program it to use these 'illegal' subnets.
> I am just wondering if the Ascend product will properly recognize a
> 208.133.27.0/27 as a subnet and not as the entire class C :)
They will. The cisco will if you use "ip classless". The routes should
be propagated with RIPv2 for this to work as expected. This requires
Cisco IOS 11.1 (AFAIK). You could try OSPF, but grep the archives of this
list on OSPF before - you have been warned.
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