Subject: Re: Serial and SSH - conections over network
To: Chuck Yerkes <chuck+nbsd@2003.snew.com>
From: Steven M. Bellovin <smb@research.att.com>
List: netbsd-users
Date: 07/10/2003 20:26:45
In message <20030711002132.GA26289@snew.com>, Chuck Yerkes writes:
>Quoting Maurizio Caloro (mauric@gmx.ch):
>> i put my sparc now in my garage because its a little too loud :-),
>> and i manage it over  the (electric-network stromnetzwerk)
>> over ssh and its where good, any my little network 14mbit its fast enough !,
> 
>> but any time my sparc after a reboot dont start where fine and i must
>> walk to my garage :-( ......
>
>Why would you ever need to reboot?  I've got a sparc 2 out there with
>480 days of uptime.
>
>> now my question can i attache the serial device over LAN ??.
>> 
>> can i use it my client machine to manage my server  after a failed
>> reboot, 
>> 
>> PREMIER i want use Serial and SSH over one lan TP kable ???
>> 
>> is this possible ????
>
>Ethernet != Serial.
>You can use the same cables, but ethernet needs 4 wires and serial
>really wants 8 (you *might* get away with a 3 wire serial at 2400baud).
>But 2 CAT5 cables gives you want you want perhaps.

Also, serial devices are generally RS-232, which uses the local ground 
as a reference point.  If your garage and your house have a voltage 
differential between their grounds, this could be problematic.  (
Today's twisted pair Ethernet uses the relative voltage between two 
wires, and hence is better; even so, you're generally better off using 
fiber between buildings.  I have vague recollections of a very early 
coax Ethernet standard being revised because of some dangerous ground 
current issues.)

		--Steve Bellovin, http://www.research.att.com/~smb (me)
		http://www.wilyhacker.com (2nd edition of "Firewalls" book)