[mdlug] IPCOP install

[Joseph C. Bender]

Tony Bemus wrote:
> I believe you can not because the 192.168.x.x ip range is a Class C
> range with a default subnet mask of 255.255.255.0.  If you need to use
> the 255.255.0.0 subnet then start with a class B address like
> 172.16.x.x 
> 
	
Please go and read RFC1918 (http://www.faqs.org/rfcs/rfc1918.html). 
192.168.0.0 is a /16.  172.16.0.0 is a /12, NOT a /16, despite so many 
references getting it very very wrong.

I will also point out that Class A, B and C are very outdated 
nomenclature, as CIDR's been in effect for many years now.  It's more 
common to refer to networks by their CIDR bitmask (/16, /20, /19, /24).

The 3 private subnet allocations are as follows (from the RFC):

10.0.0.0        -   10.255.255.255  (10/8 prefix)
172.16.0.0      -   172.31.255.255  (172.16/12 prefix)
192.168.0.0     -   192.168.255.255 (192.168/16 prefix)

So, to answer David's question, yes, you can use 192.168.0.0/16 
(255.255.0.0) as a unpartitioned subnet.  I wouldn't advise doing that 
(just because it's a massive subnet that doesn't need to really be that 
big), but you can do it.  If you really want to allocate /16s everywhere 
and keep it in the same overall IP supernet structure, do it in 
10.0.0.0/8 space, start from the bottom and work your way up.  This is 
very useful, as it permits for simpler things like firewall rules 
addressing the supernets for things like outbound NAT rules.

David, if you want to see how various ip masks and combinations work for 
various things, try installing ipcalc on your favorite linux distro. 
It's a little command line widget that for a given network address and 
subnet mask (or bits) will give you lots of useful information.  I use 
it all the time to double check my work when I'm splitting out IP 
supernets into funky subnets that I can't always recall precisely.

HTH



-- 
Joseph Bender
Bendorius Consulting
P: 248-434-5580
F: 248-434-5581
jcbender at bendorius com