Multiple serial consoles via null modem cable

[Michal]

On 12/01/2010 16:08, Jeremy Chadwick wrote:
> On Tue, Jan 12, 2010 at 05:14:44PM +0200, Marin Atanasov wrote:
>> Hello there,
>>
>> I'd like to ask you about the following - is it possible to have multiple
>> serial consoles coming from a single host?
>>
>> What I am talking about is connecting multiple machines using a null modem
>> cable - I know it is possible only to connect two machines and they need to
>> be connected on sio0 (COM1).
>>
>> I'm thinking about the following situation - 1 system acting like a host
>> with a serial port hub, each port of the hub is connected to a different
>> machine on sio0, using null modem cables.
>>
>> This would make the first machine something like a cheaper kind of a
>> terminal concentrator :)
>>
>> What do you think, have someone tried this and is it possible at all?
> 
> What you're describing is basically the concept of a serial console
> server, where a FreeBSD box contains a multi-port serial card that's
> connected to multiple other servers.  An individual would get on the
> FreeBSD box with a multiport serial card (see below) and attach to the
> serial port associated (wired to) whatever other box they want to log on
> to.
> 
> Yes this is possible with FreeBSD -- but you'll need to purchase a
> multiport serial card that's supported natively by FreeBSD.  The two I'm
> familiar with are Cyclades and DigiBoard, but this would've been back in
> the day of FreeBSD 2.2.x and I've no idea what people use present-day.
> I'm certain others here can recommend stuff that works.

<snip>

You've actually mentioned one here, Digi. They make console devices and
I've used, with great success. Ours had modems as well so we had a
normal TCP and a phone line for DR. There is a range of sizes, SSH2 and
some have 2 psu's. They have American as well as European providers,
though I can't remember where we purchased ours from. We didn't use ours
on servers however, they where just for switches, routers, load
balancers et al so I can't comment on how well they worked with those,
but I can't see it being any different.

http://www.digi.com/products/consoleservers/digicm.jsp