[HECnet] Connections?

[dwe-6006 at philtest.org]

The case of multiple simulated systems talking to each other as well as talking to the host is pretty simple but it does require that the guests and the host all have unique IP addresses. In this case just set up software bridge that connects tap devices for each guest to the physical Ethernet adapter for the host. The guests can have unroutable addresses as long as the host understands that they exist on the bridge. It’s less ugly if the host has a secondary address in the unroutable subnet but brute force will work nicely if necessary.

 

Where the multiple simulated systems need to speak to each other and the host and the Internet, the easy way is the tap and bridge solution  but all the devices require unique and routable IP addresses.  Where routable IP addresses are at a premium then the tap and bridge alone will not work and the options range from NAT (which can be painful) to  using one of the software virtual routers like dynamips running a suitable version of Cisco IOS or the DD-WRT appliance (which can also be painful)

 

Dave

 

 

 

From: owner-hecnet at Update.UU.SE [mailto:owner-hecnet at Update.UU.SE] On Behalf Of Mark Pizzolato
Sent: Saturday, May 5, 2018 1:56 PM
To: hecnet at Update.UU.SE
Subject: RE: [HECnet] Connections?

 

Hi Mark,

 

I’m not understanding what you saying here.  

 

Are you suggesting that on a single host system, you’ve got multiple independent simulators running which all are using the same IP address as the host system? And, if true these devices can then, not only uniquely communicate with remote systems (on the Internet say), and also to each other AND the host system?

 

-          Mark

 

From: owner-hecnet at Update.UU.SE <mailto:owner-hecnet at Update.UU.SE>  [mailto:owner-hecnet at Update.UU.SE] On Behalf Of Mark Abene
Sent: Saturday, May 5, 2018 10:45 AM
To: hecnet at update.uu.se <mailto:hecnet at update.uu.se> 
Subject: Re: [HECnet] Connections?

 

This is an often misunderstood generalization, with some people able and others not. I remember this being true on *BSD. You could not connect to a simulated IP on the same host. It *used* to also be true on Linux, but is no longer the case for some time. On my ubuntu server where I run dynamips, simh, and klh10, all on bridged taps, I can telnet to all instances, even locally.

 

-Mark

 

 

 

On Sat, May 5, 2018, 12:27 AM Johnny Billquist <bqt at softjar.se <mailto:bqt at softjar.se> > wrote:

On 2018-05-05 03:39, Robert Armstrong wrote:
>>since once Multinet grabs the interface, I can’t get to the underlying 
> host.
> 
>    Actually I think it’s a limitation in simh and the pcap library – the 
> simh guest OS can’t talk to the host OS on the same interface.  You can 
> work around the problem with a TAP device.  Check the archives for the 
> simh mailing list – it’s been discussed many times before.

No. That is not correct. I run simh myself on a machine where I have 
both the native host and simh talking on the same ethernet. And they are 
both reachable by other hosts.
The OP must be doing something else funny.

   Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se <mailto:bqt at softjar.se>              ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

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