Re: How to address hosts in dual ethernet networks?
On Thu, Oct 04, 2012 at 05:01:13PM +0200, Robert Latest 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.
>
Using rfc1918 address space is fine. That's what they are there for.
"can't make any assumptions" here is your mess! Where is the responsible
person to talk to, how your network is designed and which subnets are
assigned and which are still free for use? But the phrase "multinational
corporation" does not instill hope. I worked for several of those and
usually the network is handled by college aged kids who graduated from the
geek squad. They click through some menues on M$ server machines until it
somehow works, but they have no clue what they are doing. Usually the
networks are flooded with broadcast packages and ICMP. Also the drop rate on
their routers sometime exceeds 50%.
> 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.
>
> > The devices on your modbus should be assign a unique IP address which
> > MUST NOT overlap with any other range already in use at your place.
>
> Got that.
>
Good luck then.
--
Henning Follmann | hfollmann@itcfollmann.com
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