problems with network setup sis900 in 10baseT mode

Dagmar d'Surreal dagmar.wants at nospam.com
Tue Jul 29 13:16:18 PDT 2003


On Tue, 2003-07-29 at 12:50, Rob van Dam wrote:
> I finally got it working I used the following startup script:
> 
> ifconfig eth0 up 10.0.0.159 netmask 255.255.255.0 
> sleep 5
> mii-diag -A 10baseT-FD eth0
> sleep 10
> mii-diag -A 10baseT-FD eth0
> sleep 5
> 
> After the "random" script I start up dhcpcd.
> 
> And yes everything works perfect!

Doubt it.  Without the proper number of twists in the cable a nearby
hair-dryer or car with a noisy electrical system (for two examples) is
going to murder your throughput.  The fact that the network card and
hub/switch aren't negotiating properly should be your first sign that
there's some serious signal loss taking place.

Note, I'm not trying to come down on you in particular, I just want to
make sure the other people reading on the list understand that this is a
+very+ bad thing to do and will always cause massive headaches.

> >That's a shame.  Try something wireless.  Telephone cable is not
> >ethernet.  I'd catch hell on this list if I told you _exactly_ what I
> >thought of someone trying to run 10base-T over telephone cable...
> >although in this case I suspect the vast majority of them are thinking
> >the exact same thing.  If you want to use that wire, stick a 33.6k
> modem
> >on each end.
> 
> Wireless modems have a reach up to 100 meters through free air (not
> through walls etc.) So this is no option to me.

They go through walls, just not as far.  Masses of people (who contain
much water) do a much better job of interfering with the signal.  Search
Google for "pringles can wireless" for a _cheap_ solution to extending
the range of a wireless network.  (I frequent a coffee house that has
wireless and we can use the AP there from the porch outside with no
problems, and literally 150 yards away from the building with a pringles
antenna.)  Seriously, a pringles antenna is so cheap if you can find two
people with notebooks and 802.11 cards you can do a little
experimentation (and probably scare some people who thought their AP was
secure in the process).

In any case, unless that under the street conduit was laid with no room
to spare, any decent electrician could probably run a snake through it
to pass a new cable across.  (Might be something to keep in mind for
possible upgrades to 100mbit)
 
> >> It works perfectly in Windows so why should it work under Linux?
> 
> >"It works perfectly in Windows" is a lame response and don't expect me
> >to fall for it.  Generally the only reason people get this idea is
> >because Windows doesn't let them notice how _badly_ things are
> performing.  >Additionally... I am _pretty damn certain_ that it is
> *not*
> >working perfectly under Windows.
> 
> Not for me. It was the proof that it must be possible to get everything
> working, and a big motivation to keep on trying. 
> 
> And it works, believe me. (I spend hours on internet by now, downloading
> lots of stuff for example a complete Mandrake distribution, without
> problems)

Just wait for your first electrical storm, construction on the street,
or someone operating a power drill nearby.

> >Cisco can get gigE over old coathangers, but you are clearly not them.
> >If you want to run your network over piano strings and foil bubblegum
> >wrappers, that's your decision, but don't expect other people to
> support
> >it. 
> 
> I am not an expert, but I read several sites explaining that a 10 mbit
> network is possible through telephone cable, because a 10 mbit network
> doesn't cause much interference etc. and 100 mbit does.

You should read more carefully then.  100mbit does not _cause_
interference--it's much more susceptible to interference because of the
increased complexity of the signal involved.  10mbit will behave fine on
an improperly wired cable (i.e., when the pairs aren't matched up so
they don't twist around each other, as when people mistake something
wired as an RS-232 extension for an ethernet cable) provided there is
almost _no_ electrical noise nearby.  Put them anywhere near something
that generates a little bit of RFI (like an extension cord, or gods
forbid, a fluorescent light) and packets will simply cease to traverse
the wire.  I've been tanked before by someone putting a radio alarm
clock _near_ a miswired cable. [1]  Those sites should probably mention
that it will only work with _some_ phone cables, as not all telephone
cable has the pairs twisted, as it is not required.

With a _properly wired_ cable you can hang the 10base-T segment along
the same hooks as an active string of common christmas lights and it
won't be bothered (done that, too.  heheh).

[1] Sidebar... Those cool looking "plasma balls" one finds for sale in
gift shops generate enough noise to stop half a rackful of switches
cold, proper cabling or not.  You don't want to know how I know this.
-- 
The email address above is just as phony as it looks, and for obvious reasons.
Instant messaging contact nfo: AIM: evilDagmar  Jabber: evilDagmar at jabber.org




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