Well, if the network isn't connected to the Internet, and isn't going to
be, then you can use whatever addresses you like. Not recommended to use
any old class A (just because requirements always change - you may have to
merge with another network, you may need Internet connectivity in the
future etc), but it will work.
You can use NAT (Network Address Translation) or PAT (Port Address
Translation) to translate your 'inside' network addresses (i.e. anything
you choose) to legal assigned Internet addresses. This can be done either
statically or dynamically. Not all protocols work with NAT; for example if
the IP address is contained in the data portion of the application packet,
NAT needs to be aware of that and needs to change it there as well (which
may mean re-calculating checksums etc - messy).
It is generally recommended (actually, I think it is universally
recommended) that if you have a choice, use RFC1918 Private addresses if
you're not using 'real' (i.e. allocated to you) addresses. These are
address blocks set aside and not allocated to anybody. 10.0.0.0/8 is the
class A address defined as a 'private' address block.
Why might you use some other class A? Well, we use multiple unassigned
class As in our internal network. It makes it easier to have an addressing
scheme that uses the octet boundaries - you don't need to be able to think
in binary to be able to work out what office a particular address refers
to. On its own, that isn't a very good reason - but our network addressing
scheme was implemented before RFC1918 came out, and it's a large,
geographically distributed network with several hundred remote sites (very
remote, some of them). The effort and pain that would be involved with
re-addressing is, so far, greater than the effort and pain in working
around the problems caused by using 'illegal' addresses. Sooner or later
we're probably going to have to readdress, but personally I'm hoping
somebody comes up with some other solution ;-)
JMcL
-- Forwarded by Jenny Mcleod/NSO/CSDA on 16/01/2001
12:37 pm ---
Jennifer Cribbs [EMAIL PROTECTED]@groupstudy.com on 16/01/2001
10:21:57 am
Please respond to Jennifer Cribbs [EMAIL PROTECTED]
Sent by: [EMAIL PROTECTED]
To: "John Pusledzki" [EMAIL PROTECTED]
cc: [EMAIL PROTECTED]
Subject: RE: subnetting and tcp/ip and Private addressing Help!
There is such a thing as private addressing where you can have any address
you
want, but you usually have something set up at the router that dynamically
assigns you an address space when you leave your network, such as out in
the
internet world. That way you remain legal... And the addressing within
your
network is your own business then. I do not know how this actually works,
but
I do know this is an option. I think I read something about NAT providing
this service. The group would know about this. I do not. Chuck is a
good
one to ask on this issue...
The question is how come someone can have a class a address that internic
did
not assign. Anybody??
Jen
Have a Good Day!!
Jennifer Cribbs
[EMAIL PROTECTED]
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