[Simh] Networking through multiple layers of emulation
Hittner, David T (IS)
david.hittner at ngc.com
Tue Nov 10 11:49:32 EST 2009
Well, the simplest way is to not use DHCP - hard set the IP address
using TCP$CONFIG.
Various versions of DEC TCPIP did/didn't do DHCP very well. That could
be part of your problem.
You can see the MAC address of the nic with "show xq mac". You can
change this with "set xq mac=xx-xx-xx-xx-xx-xx".
Wireless Ethernet is not standard ethernet - it looks like Ethernet, but
has many behavioral differences, DHCP being one of them! Wireless
ethernet first has to register a mac address, then it DHCPs it. Many
wireless cards and routers refuse to tolerate multiple mac addresses
coming from the same physical wireless port.
Dave
-----Original Message-----
From: simh-bounces at trailing-edge.com
[mailto:simh-bounces at trailing-edge.com] On Behalf Of Susan Mackay
Sent: Tuesday, November 10, 2009 4:46 AM
To: Larry Baker
Cc: simh at trailing-edge.com
Subject: Re: [Simh] Networking through multiple layers of emulation
Larry and others who have responded to my posting.
Just to get it out f the way, I'm using this rather complex
arrangement because the last time I used the 'simh' program directly
under OS X, I couldn't communicate with the host computer - and I
don't have another computer I can use to access it. I tried using the
Tap/Tun method but that doesn't seem to work (or at least I couldn't
get it to) under OS X.However Parallels allows me to talk between
virtual machines and between the VMs and the host - just what I'm
trying to do. I don't want a VM guest OS like Windows (can't afford it
just for this purpose) which is why I chose FreeBSD.
I'ved used the TcpDump (thanks for the suggestion neozeed) and I can
see that the DHCP request is being sent and a response passed back
from the DHCP server. however it does not appear to be heard by the
simh/OpenVMS combination as nothing happens after that.
I noticed that the MAC address I set in simh is different to the one
used by the FreeBSD interface and is different again to the one the VM
is offering. Finally, the DHCP server device shows a list of the
addresses it has given, and the MAC address it lists against the
FreeBSD environment is that of the OS X host, and none of the other
MAC addresses!!!!!
I'm still trying to learn about this level of networking stuff, but I
understood that the DHCP messages are transferred using MAC addresses,
there being no IP address for the DHCP service to talk back to (at
least at the start of the exchange). If that is so, is there some way
I can see the MAC addresses that are being passed between OpenVMS/simh
and the DHCP server? I suspect that something somewhere is giving or
sending the wrong MAC address and so the response from the DHCP server
is getting lost.
Of course, if there is a simpler way, I'd love to hear about it. (It
had better be simple if I'm to understand it!)
Thanks for the assistance.
Susan
On 10/11/2009, at 05:52, Larry Baker wrote:
> Susan,
>
> I'm not sure if your motivation is to study multiple layers of
> emulation or not. But, if not, it might be quicker for you to just
> run SIMH directly on your Mac. Many of us have compiled SIMH for
> Macs to run OpenVMS. Give it a try.
>
> Larry Baker
> US Geological Survey
> 650-329-5608
> baker at usgs.gov
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