[SunRescue] Networking details (was Re: OT: Advice on Certification)

[Robert Novak]

On Sat, 5 May 2001, Jonathan Katz wrote:

> Nick asked:
> 
> > second question, isn't 192.168.1.0/16 invalid?  shouldn't it be
> > 192.168.0.0?
> 
> *nod* It should.

Well, 192.168.1.0/16 is a valid ip address and netmask. In the
192.168.0.0/16 network, 192.168.0.0 is network and 192.168.255.255 is
broadcast, so anything else in the middle *could* be used.

This may confuse systems that don't understand CIDR; we had some issues
with our /22 subnet internally at work, wherein the dhcp server assigned a
middle-appears-to-be-24-bit-network .255 address and it caused some
serious problems. 

By the way, I have to ask for sense of completeness (and I apologize for
not pasting the citation):

> Ahh yes, however how many are familiar with what "Class C" actually means,
> rather than the common misconception that it means "/24" or 255 ips, or
> any number of other ways to say it? <grin>

Are we talking 192.0.0.0-223.255.255.0 networks that are /24 by default in
a classful network structure? That is the best definition of a Class C
*Network*, but I think "Class C Subnet" is clear enough to mean a /24
regardless of what it is a subnet of. 

I'd be far more worried if someone didn't understand what I meant if I
said "break down 69.0.0.0/8 into class C subnets" ... and if someone in
an interview said "you can't do that because that's a class A network and
it's reserved anyway" I'd show them the door.

The vernacular may be impure, but how many of you work in Latin on a daily
basis in your NOCs? :-)

Rob
-- 
Robert Novak, Indyramp Consulting * rnovak at indyramp.com * indyramp.com/~rnovak
        "And it's been a long December and there's reason to believe
           Maybe this year will be better than the last...." -- counting crows