NetNews Usenet Archive 1992 #27/NN_1992_27.iso/spool/comp/os/vxworks/1015

Internet Message Format | 1992-11-16 | 3.1 KB

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Newsgroups: comp.os.vxworks
Subject: Ethernets and backplane networks
Date: Mon, 16 Nov 92 12:35:16 GMT
Organization: Lawrence Berkeley Laboratory, Berkeley CA
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We have come up against a problem that I am sure other VxWorks users will
have encountered and overcome lots of times already, I would appreciate it
if you would pass on any thought on this subject.

We have a VME crate with a mv147 connected to a Sun Sparc via thinwire
ethernet. The Sun has two etherent ports, and is connected to our factory
ethernet (and via that to the world) using the standard thickwire ethernet.
The reason for having the mv147 on a separate ethernet is that it reduces
the network traffic on that ethernet, and thus Sun to mv147 communications
is faster. We intend to manufacture and ship a number of products based on
this sort of configuration.

The problem is the internet numbers. We use class C internet numbers and
have had to split our factory ethernet into two networks as we had run out
of node numbers, thus we have 192.23.1 and 192.23.8 network numbers. It is
my understanding that the Sun with two ethernet ports needs to have two
internet addresses on different networks, so the mv147 will be on a new
network (eg. 192.23.9). This is fine for a one-off, but when we have a
number of these in production, or ship a number to a single customer, we
would be using up internet network numbers at an unacceptable rate
(unaceptable to both us and the wider internet community).

There is a similar problem with a configuration that consists of a Sun with
a single ethernet interface, the mv147 is on the same ethernet/network but
has a backplane network. In this case the mv147 has two internet numbers:
the ethernet and backplane.

My questions are:
Can we physically split a single internet network, ie. have a network number
dedicated to the 'private' mv147 networks for all systems configured like
this, and use different node numbers on each system, all connected to the
same ethernet at the same time ?  (To make this clearer an example:
On the factory ethernet connect two Suns: 192.23.1.100 and 192.23.1.101.
Each Sun has two ethernet ports, the thinwire ports are 192.23.9.1 and
192.23.9.11. The associated mv147s are 192.23.9.2 and 192.23.9.12.)

The other option seems to be subnetting. Does anyone have experience with
this on VxWorks ?

Is there any other way of getting over the problem of using up internet
network numbers ?

Thanks in advance...
            Bill

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Bill Frewing
Schlumberger Technologies        Phone: [phone]
Ferndown Industrial Estate        Fax:   [phone]
Wimborne, Dorset, BH21 7PP        Email: [e-mail]
United Kingdom
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