What IP addresses should I use for a cluster?

[Robert G. Brown]

On Wed, 16 Sep 1998, Alex Ingerman wrote:

> Hi,
> 
> The choice of internal IP addresses is not really important, as long as
> they are in the reserved internal IP ranges. I myself prefer to use
> 222.222.222.x - they make things much easier to remember, just give your
> computers numbers '1', '2', '3', etc. Of course the 198.68.x.x gives you a
> higher class of IPs available... but my networks rarely exceed 3 machines
> :)

This is wrong.  (Ahh, RFC's strike again:-).  The reason to use
192.168.x.x addresses is that this class B subnet is RESERVED by an RFC
(can't remember which one) for private networks.  This is incorporated
into router design.  Routers are guaranteed NOT to forward and handle
192.168.x.x IP addresses, so private remains private.  If you ever screw
things up and your internal packets make it onto a real network, the
real owners of 222.222.222.x will be kind of pissed off when WAN IP
routing gets somewhat confused (remember, most routers build tables
dynamically).

So, if you are building:

a) A beowulf on an inner LAN with a dual-hosted member gatewaying onto
an Internet-connected WAN;

b) A private corporate network inside a firewall;

c) An IP forwarding/IP masquerading LAN (like a home network with a
single IP POP)

etc. you should most definitely use 192.168.x.x.  They don't belong to
anyone (or more properly, they belong to everyone:-) and they are
guaranteed not to screw anything up if somebody comes along and sticks
your inner network on a bridge to the outer network.

   rgb

Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb@phy.duke.edu