[c-nsp] which one is ugly

Gert Doering gert at greenie.muc.de
Sat Dec 11 07:51:35 EST 2010


Hi,

On Sat, Dec 11, 2010 at 08:27:28AM +0500, Good One wrote:
> I was just thinking about using bla.bla.bla.0/32 (as a loopback
> address) and bla.bla.bla.0/31 on some point to point interfaces.
> Not sure which one is ugly and not useable at the moment. But would
> love to hear from you guys...

Both are ugly.  It's IPv4, what do you expect?

Seriously: in theory, it should just work.  

If "bla" is from the former Class C space, though, there might be 
some surprises in using the .0, as IOS has "helpful features" for the 
"oh, you are talking about the whole Class C here?" case...

Cisco-XX>sh ip route 10.255.255.0
Routing entry for 10.255.255.0/30
  Known via "eigrp 99", distance 90, metric 157696, type internal
  ...
  (showing *just* the route that decides where the .0 goes to)

Cisco-XX>sh ip route 194.xx.129.0
Routing entry for 194.xx.129.0/24, 19 known subnets
  Attached (1 connections)
  Variably subnetted with 3 masks
  ...
  (showing all subnets, not just "where would you route the .0 to?" - which
  is especially annoying because the actual route for packets to ".0" is
  not even showing up in this example's output, as the .0 would be part of 
  the 194.97.128.0/23 supernet...)


I'd *really* wish Cisco would notice that the days of Class C networks
are gone, and that ".0" has no more or less special meaning in "former 
Class C" space than in "the rest of the legacy IP address space"...

gert
-- 
USENET is *not* the non-clickable part of WWW!
                                                           //www.muc.de/~gert/
Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de
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