[Simh] The Ultimate SIMH VAX Networking Challenge!

[Robert Jarratt]

> -----Original Message-----
> From: simh-bounces at trailing-edge.com [mailto:simh-bounces at trailing-
> edge.com] On Behalf Of Seth Morabito
> Sent: 04 July 2009 22:50
> To: simh
> Subject: [Simh] The Ultimate SIMH VAX Networking Challenge!
> 
> Hey everyone,
> 
> I've got a puzzler for the more experienced SIMH users here who might
> already be doing what I'm trying to do.
> 
> My end goal is to have a single host system, with a single physical
> Ethernet, hosting two (or more!) SIMH VAX instances. Each SIMH VAX
> should be able to communicate with all the others, and with the host,
> and all of them should be reachable from the public Internet.
> 
> So, for a concrete example: Assume the host has a single ethernet,
> eth0, with address 192.168.0.100. The two simulated VAXen should have
> addresses 192.168.0.101 and 192.168.0.102, and be able to communicate
> with the host, with each other, and with anything else on the
> 192.168.0.0/24 network.
> 
> I've been trying to wrap my head around various techniques using
> taptap.c and bridge-utils, but I have been frustrated getting anything
> to work.
> 
> For reference, here are the pages I've been studying:
> 
> http://www.retrocomputinggeek.com/retrowiki/SIMHNetworking/
> http://www.itsecuritygeek.com/itsgeek/comments/simh-modified-version-
> of-taptapc/
> 
> The technique of using taptap.c works well for host-to-SIMH
> communication, but the VAX is not routable to the outside world since
> it needs to be on its own network. Conversely, trying to use
> bridge-utils to create a tun0/eth0 bridge just causes the host to
> become unrechable on eth0's IP address (quite alarming when I was
> trying to set up the bridge remotely, and ssh simply froze up after
> adding eth0 to the br0 bridge!), so I've had no luck with that at all.
> 
> Has anyone had success doing this? I've been searching for a solution
> for a couple of days now, I've lost hope that it can actually be done!
> 
> -Seth
> --
> Seth Morabito
> Union City, CA, USA
> sethm at loomcom.com
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I don't have a TCP/IP solution but I have found that DECnet works fine even
when the simulated VAXen are on the same host (I don't understand DECnet
well enough to explain why). I would have thought that the winpcap
limitation would not affect visibility from the internet. So, although you
would not be using just TCP/IP you could achieve most of what you want with
nothing special. The only thing you would not be able to do is Telnet into
the simulated VAXen, but there again you can still telnet into the console
session.

Regards

Rob