Re: Why has my local Ethernet packed up?

Rowland McDonnell <real-address-in-sig@xxxxxxxxxxxxxxx> wrote:

Okay. It's like this:

I've got a 10.3.9 G4 and a 10.4.7 G5 and an HP LJ 1320n printer.

I've also got a gigabit switch and a 10/100 hub (both unmanaged Netgear
jobs).

They're wired up as follows:

G4 and G5 to the Gb switch. The Gb switch to the 10/100 hub. The
10/100 hub to the printer (and it'd also be connected to the iBook, but
the iBook's not here at the moment).

Now, up until this morning, everything `just worked'. All the cabling
was Cat5e.

This morning, I got some new Ethernet cables.

I put a Cat6 0.5m patch cable between the G5 and the Gb switch, one of
the same between the Gb switch and the 10/100 hub, and put the Cat5e 2m
cable that I'd previously used from the G4 to the hub (before the Gb
switch and G5 arrived) to run from the G4 to the Gb switch.

Sounds like MDI/MDIX issues.....


This is exactly the same topography I was using yesterday: only the
cables have changed.

The lights on the hub and switch imply that I've got `live' links
everywhere you'd expect to see 'em.

When I did the cabling changes, the hub, switch, and printer were on,
the G5 was off, and the G4 was sleeping.

The port lights on the Gb switch are `on' where there is a cable running
to a `live' device. Ditto the hub.

Nothing can see anything else via the Ethernet links any more.

Argh. No, scratch that. I just re-tested before I sent this: it now
seems that the G5 and G4 can see each other. They are now filesharing
to each other happily.


So devices on the gig switch can see each other. but the gig switch
can't see the hub. There is a connection problem between the switch and
hub.

But the flippin' printer still seems to be invisible (N.B. the G5 and G4
are plugged into the same Gbswitch; the printer's connected via the
10/100 hub hung off the switch. Yes, there's no particular reason why I
shouldn't plug the printer into the switch at the moment, but that's not
the point, really, is it? It should `just work', am I right?)

In itself, yes. But....

When you connected the switch and the hub together previously, did you
use a crossover cable? And have you remembered to use the same cable
between the two again?

When connecting repeating devices together, you need to swap the send
and receive pairs, so that one device sends to the other devices'
receive pair. This is done either with a crossover cable, or with an
MDI/MDIX switch on /one/ of the switch or hub.

Confusion can arise when manufacturers 'helpfully' give you autosensing
ports, especially if they're on both ends. They both autosense, cross
themselves over, then shut down because neither think they can get a
working connection.

Try:

- Check the Switch and Hub, to see if there is an MDI/MDIX button. This
usually applies to one specific port, and it's nearly always the first
or last one, and may be marked 'uplink'. Make sure that the connection
between switch and hub uses this port. Check connectivity, and if
there's no joy, flick the switch. 99/100 times, this fixes things.

- if not, check your cables. Make sure they're all straight-thru leads.
looking at the RJ45 connector, with gold pins up, the wires should run

white-orange
orange
white-green
blue
white-blue
green
white-brown
brown.

left-to-right.

If they are in a different configuration, you have a crossover lead, and
this is confusing matters at the moment. For the record, when looking at
a crossover lead with the gold pins upwards, the order is

white-green
green
white-orange
blue
white-blue
orange
white-brown
brown

left-to-right.

- next, is your switch a managed device? Can you either telnet to it, or
does it have a web-based configuration system? If it does, check the
settings for the port that connects to the hub. You may be able to set
the crossover behaviour there (straight-thru/crossed/autosensing). If
it's not a managed device, there will probably be a marked Uplink port
on it as mentioned before.

If neither switch or hub is managed, and doesn't present an uplink port
to you, you need to connect them with a crossover lead.

I have looked at the printer and it is indeed switched on (well, the hub
light for its Ethernet connection kind of showed that, didn't it?)

I've tried switching the printer off, leaving it for `a few minutes' and
switching it back on again - nuffin'.

The HP utility for the printer cannot see the printer - well, I say
`utility', all it is is a url to the printer's built in Webserver: it's
apparently not there.

I've fired up `Bonjour browser', and it shows an exciting list of
available services[1], none of them resembling anything to do with
printing.

Can anyone explain what on Earth is going on and what I should do about
it? I don't have any chickens or goats for a sacrifice, I'm afraid.

Cheers,
Rowland.

[1] No, I can't think what came over me.


--
james dore
new college
it-support@new/james.dore@new
http://www.new.ox.ac.uk
.

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