[Simh] The Ultimate SIMH VAX Networking Challenge!

[David Holland]

The short version, Under Linux,

tap devices, taptap, and boring old routed networks seems to work just fine.


eth0 - Internet facing interface.    (IP Address assigned via DHCP)
tap0 - DMZ interface.                  192.168.4.1 (Static assignment.)
tap1 - Tap Device for SIMH.        192.168.4.20 (As assigned in TCPWARE)

taptap "connects" tap0, and tap1.

VMS's default gateway is via 192.168.4.1.

tap1 is _NOT_ assigned an IP address from the Linux perspective, but it must
be flagged as "up".

However, this configuration wouldn't work for DECNET

The "usual" method for same subnet (read: DECNET) is to use bridges, and
taptap.

br0
contains eth0, and tap0
stp is turned off.

>From the linux perspective:

eth0 -> 192.168.x.x
tap0 -> (no IP) but must be UP.
tap1 -> (no IP) but must be UP.

taptap "connects" tap0/tap1.

tap1 is used by SIMH/VMS.

No idea how to do this under Windows, but it should be theoretically
possible, with the OpenVPN tap interface drivers for Win32.

David


On Sat, Jul 4, 2009 at 5:49 PM, Seth Morabito <sethm at loomcom.com> wrote:

> 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
> _______________________________________________
> Simh mailing list
> Simh at trailing-edge.com
> http://mailman.trailing-edge.com/mailman/listinfo/simh
>
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