[Simh] VMS/VDE: Almost there

[Mark Pizzolato - Info Comm]

On Monday, October 5, 2015 at 8:58 AM, Jordi wrote:
> >>
> >> Johnny, VDE works at layer 2 and has no idea about IP addressing or
> routing.
> >
> > Right. But the point was that the VDE should be between just the simh and
> the MAC, and not bridged with the WiFi. Sounds like it is bridged to the WiFi
> in this case…
> >
> Oh, you mean using the mac as a router (ip forwarding enabled). Then you
> are right and the mac itself would have to provide DHCP services to the “tap”
> interface where the virtual switch is accesible. TBH I’ve never tried this
> myself, and I’d advise to use static IP configurarion in the VMS side.

Actually getting the 'mac as a router' to work would be far more complicated since router on the LAN would then need to know about the additional network that the mac was routing for.  Getting this to work would, at least, be complicated for a single router and never for the general case.

The NAT approach (which slirpvde can implement) allows the rest of the network (the WiFi router) not to know that any of this going on.

The goal here is to come up with a recipe that allows a user to just "attach" his LAN device via NAT and just have it work.  This would allow many simh users who may not be network engineers to actually get things working easily.  VirtualBox and the various other system emulators all have a simple NAT network setting which is usually the default and just works.  It just works for most cases since the common case is to get basic IP networking up and running.  The harder case is DECnet, but we already know how to do that (via a bridged model).

- Mark