Message trimmed for brevity comments are added inline.
On Sun, 2008-11-23 at 15:33 -0500, Simón Ruiz wrote:
> Hm. Most consumer routers I've seen are set up for the 192.168.1.0/24
> subnet, IIRC. Another non-spec standard?
>
> > Imagine a public school that has a simple network of 172.16.0.0/20 and
> > they need to integrate into a statewide network. I am sure you can
> > write the routing information for that on a piece of paper. A well
> > defined network is easy to route, manage, and understand.
>
> Our network is well-defined, it's just well-defined outside of RFC
> spec, apparently, because we use the 10.0.0.0/8 range and it's not all
> crammed together in one humongous subnet.
>
You network sounds like it should be setup correctly lets not get our
RFCs confused. If you were operating a classful network then yes you
would be having issues but you probably aren't. Your probably using a
classless (CIDR) network which is "right" in todays network. In my
professional opinion if you have equipment that is not capable of being
classless then I build a walled garden around that piece of equipment to
get it to talk to the rest of the network as opposed to design an
archaic network structure around a single or limited devices. Snip from
RFC 1918:
<snip>
3. Private Address Space
The Internet Assigned Numbers Authority (IANA) has reserved the
following three blocks of the IP address space for private internets:
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)
We will refer to the first block as "24-bit block", the second as
"20-bit block", and to the third as "16-bit" block. Note that (in
pre-CIDR notation) the first block is nothing but a single class A
network number, while the second block is a set of 16 contiguous
class B network numbers, and third block is a set of 256 contiguous
class C network numbers.
</snip>
So lets understand that these are just reservations in the IP address space and
are not in any way tied to classes other than the fact that the 10.0.0.0
reservation happens to line up with a complete Class A Network.
So prior to CIDR you netmask, network address and broadcast address were
determined by the first octet of you ip address from the following table:
Class
Leading bits
Start
End
CIDR
prefix
Default
subnet mask
Class A
0
0.0.0.0
127.255.255.255
/8
255.0.0.0
Class B
10
128.0.0.0
191.255.255.255
/16
255.255.0.0
Class C
110
192.0.0.0
223.255.255.255
/24
255.255.255.0
Class D
(multicast)
1110
224.0.0.0
239.255.255.255
/4
not defined
Class E
(reserved)
1111
240.0.0.0
255.255.255.255
/4
not defined
Let me state again this should be obsoleted by RFC 1518 & RFC 1519 and
hopeful no one who has a choice is running their network based on this
table.
>
> I thought you said the 172.16-32.*.* range was meant for 12 bit subnets,
> though.
>
> I'm a little confused, now; how would splitting that range into 20 bit
> subnets be any different than us splitting the 10.0.0.0/8 range into a
> bunch of smaller 16 and 24 bit subnets?
>
Lets be careful here and make sure we are not getting host mask and net
mask confused the RFC snippet above is talking about 24bit host mask for
the 10.0.0.0 reservation leaving an 8bit net mask remember this is just
for the reservation of space and should not limit the net mask used in
operation you in theory could use a 10.0.0.0/30 network in the
reservation fine. (Though I have found some consumer device that
seemingly cannot handle any network smaller than a /24 network. Again
return this equipment, open a ticket, or replace it because as far as I
am concerned it is broken.)
> Not likely in the least. As little as possible; I try to assign
> "static" IPs via DHCP as much as possible. There's one in each subnet
> that has workstations. Because I've never heard of it.
Great to hear that you are using DHCP for static assignments this will
greatly ease any transition where you network needs to grow or be
incorporated in to a larger network.
Well hopefully I have not added any more mud to the water and things are
little clearer now. The next big hurdle in most network designs is
routing and routing protocols. :)
HTH,
Ben
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