Re: How to address hosts in dual ethernet networks?
On Thu, 4 Oct 2012 17:01:13 +0200
Robert Latest <boblatest@gmail.com> wrote:
> On Wed, Oct 3, 2012 at 7:45 PM, Henning Follmann
> <hfollmann@itcfollmann.com> wrote:
> > The network design at your place seems like a mess and the best
> > advice I can give you is to clean that up BEFORE you do anything
> > else.
>
> What's the mess? That the Intranet contains 192.168... addresses?
> Anyway, this is a big multinational corporation, and I can't have any
> situation where the Intranet "sees" my Modbus devices, and I can't
> make any assumptions about addresses being or not being in use in the
> Intranet.
>
> I understand that from the viewpoint of my control PC I can't have any
> duplicate addresses because that's how IP addresses work. That was my
> basic question, and it was answered. So as long as I put my modbus
> stuff into an IP address range that I don't need on the intranet, and
> I make that address space "invisible" on the intranet side using a
> netmask, I'm fine.
>
Absolutely right, I and possibly others had the impression that the
same network address might be in use on both sides of a router, and that
this was beyond your control.
There are other private network addresses than 192.168., the 16 x
172.16. to 172.31. networks each have over 65,000 addresses available,
and for some reason these networks are not often used in corporate
systems. The 10. network is an /8 ('class A') and has 16 million
addresses, but I prefer to avoid that one, as I've seen a few odd
results when used with smaller subnets.
Joe
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