[plug] IP address

Matt Bruce Matt.Bruce at alphawest.com.au
Sat Aug 21 11:44:09 WST 1999


Jon,

I think it's good practice to use the 192.168.0.0/24 range when implementing
a network with only a small number of machines, though you're by no means
limited by it. Bear in mind, though, that this range is actually a B-class
with a C-class subnet mask, so even those rules are a little askew.

The B-class unroutable is 172.16.0.0/16, but noone seems to use it anymore.
Probably because it can all be covered with a 192.168.* or 10.* range.

It seems to be becoming common practice when implementing an RFC1918 LAN/WAN
to just use a 10.* network and place whatever subnet mask seems appropriate
at the time. I suppose this does have some merit, as it doesn't cost anyone
anything to, say, use a 10.* as a B-class, thereby leaving plenty of room
for further expansion on the existing segment, and allowing allocation of
further segments down the track.

Many's the time I've had to renumber a LAN or WAN, so I can appreciate where
this logic comes from. Although most of the reasons for renumbering were
because of the original implementation being set up as a 192.200.0.0/16 or
/24 because the idiots doing the work didn't bother reading the RFC (or know
or care about it). Imagine everyone's surprise when all of a sudden a site
in France goes down and everything locally stops working -- hmm, maybe
someone began routing the LAN range. It happens. DHCP (when it works) makes
this a whooooole lot easier.

There's absolutely nothing stopping you from using the whitehouse.gov IP
range in your LAN, if you really feel the need, except that it goes against
RFC1918 and will cause merry hell should anyone ever place a router on your
network (an idiot's guide to DoS? ;)). Stick with 192.168.0.0/24 or 10.*
ranges and you'll be laughing.

Catcha, :)

-- 
Matt Bruce   <matt.bruce at alphawest.com.au>
Security & Internet Engineer
AlphaWest - http://www.alphawest.com.au


>-----Original Message-----
>From: Jon L. Miller [mailto:jlmiller at wantree.com.au]
>Sent: Friday, August 20, 1999 10:29 PM
>
>I've always used the 192 range when dealing with a Class C 
>subnet, this just threw me off a little.


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