Beni Cherniavsky wrote:
>
> My home network consists of 3-4 computers and an ADSL modem all
> connected one to the other with cross RJ45 cables, with no hubs.
> This was simplest at each point in time (it started with two computers
> and one cable and at each point I had enough network cards) but it's
> somewhat inconvenient because intermediate computers sometimes need to
> be up just to pass the packets.
You could also do it wit some routing tables, for example, I assume that
you have network segment on a different subnet (shame on you if you didn't):
computer 1:
192.168.1.1
computer 2
192.168.1.2 crossed to computer a 192.168.1.1
192.168.2.2 crossed to computer c 192.168.2.3
computer 3
192.168.2.3 crossed to computer a 192.168.2.2
192.168.3.3 crossed to computer c 192.168.4.3
computer 4
192.168.3.4 crossed to computer a 192.168.3.3
10.0.1.1. connected to aDSL modem.
xx.xx.xx.xx ppp conection to isp.
This could easily be accomdated with routing,
> So now I consider adding one or two hubs. But hubs need cables that
> are not crossed. Replacing all cables would cost a non-negligeble
> price. Besides one long cable passes inside the wall and replacing it
> is out of the question. I can re-solder all cables (or re-frob the
> connectors but I don't have the device that does it) but I'd rather
> avoid the trouble.
It would be easier to get a short cable and a "punch down" wall jack
and make a 1 meter adaptor cable as needed. Cost about 50 NIS each.
> What's most annoying me about the idea is that I can see no technical
> reason for it. Why should non-crossed cables exist at all? Why can't
> the hubs have connector layout like in computers, so that
> computer<->hub cables would be crossed too and put an end to the
> confusion? What do I miss?
Some HP switches do autodetect. However every hub I have ever seen had
one port that had a a normal/reverse switch. That would cover the hidden
wire. The others could just be replaced.
Note that if you look at the plug with the wire in the back and the tab
on top pins are numbered 1 to 8 from the left. A normal cable has 8 wires
(4 twisted pairs) but only two pairs are used.
They are pin 1 and 2 pair one, pin 3 and 6 pair two.Reveresed cables
have one side the same, the other with pair twon on 1 and 2 and pair two
on 3 and 6. Wires on pins 4,5,7,8 are not used and can be cut.
Are you ever in Jerusalem? If you are I can lend you the tool and I'll
give you a handful of plugs, or you can get them sometimes at home center
or Kashayoff on King George.
> I recall that some new cards "autodetect polarity". Does this refer
> to polarity on each pair or also to Tx/Rx autodetection? Is there a
> chance that it will work with crossed cables anyway? Is it safe to
> experiment of do I risk letting the smoke out?
Never had a problem doing so, but that does not say that ALL cards
are safe to experiement.
Geoff.
--
Geoffrey S. Mendelson [EMAIL PROTECTED] 972-54-608-069
Do sysadmins count networked sheep?
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