Re: Why has my local Ethernet packed up?

James Dore <james.dore@xxxxxxxxxxxx> wrote:

A summary of my reply: it's taken bloody ages to sort through
everything. The problem was *probably* the printer throwing a temporary
wobbly. I hit it in the cold reset button and it unwobbled (all that
*after* I'd been through the cabling very carefully. I've now got
pretty coloured wires all over the floor. Tomorrow will see them tucked
away somewhere neatly.

btw, the cabling I finished up with involves a straight through patch
cable between the 10/100 switch (not hub - call me a fuckwit) and
gigabit hub and they do seem happy with it. There was a cross-over
cable I tried first - that worked too, but since the cross-over cable's
10m and I've got shorter straight through cables, I thought I'd see if
the shorter one worked. Well, it *ought* to - and it did. But at least
I know about the issues, so if I get bitten in future, I've now got a
clue what and how to check and what the issues are and all that.
Thanks ever so much.

It all seems to work fine now.

I've saved your reply for future reference - I bet it'll come in dead
handy.

Cheers!

Wot I dun follows - if you really want to know:

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.....

Righto.

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.

Could be. btw, I read the manual. it turns out that it's a 10/100
switch, not a hub. Call me a fuckwit. I could have sworn we bought a
hub, but there you go.

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?

Dunno.

And have you remembered to use the same cable
between the two again?

Erm, since I didn't know what I was using yesterday, I dunno. I *THINK*
it was `the yellow lead', which I have checked today: it's straight
through.

When connecting repeating devices together,

What's a `repeating device'?

(basically, how can I tell which devices want to have a `straight'
connection or a `cross-over' connection. Both the Macs and both the
switches claim to have all ports auto-sensing, so I had thought I could
just use whatever lead came to hand. Teach me to trust the machinery,
eh? ;-) )

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.

Righto.

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.

Ah! Righto - I do indeed have autosensing ports everywhere, pretty
much, so I wasn't paying any attention to whether I had a cross-over
cable or not. And since both the switches are from the same firm
(Netgear - the reviews seemed universal in their `it just works'ness) I
thought that while confusion seemed possible, they *ought* to work okay
together.

Thing is this:

the printer was connected to the 10/100 hub with a cross-over cable -
that had worked perfectly well up until today.

Now it just doesn't.

I've tried plugging the printer's (cross-over) Ethernet cable into the
Gb switch - no joy.

The Gb switch port light is orange on the port I've plugged the printer
into (the ports connected to the Macs get green lights).

Try:

- Check the Switch and Hub, to see if there is an MDI/MDIX button. This
usually applies to one specific port,

There's nothing except sockets - N data sockets, and one power socket.

(N=8 for 10/100, N=5 for gigabit)

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.

Ain't got one of them.

- 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.

Uhuh.

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.

Excellent - a spotter's guide to Ethernet cables: thanks! So now I'll
spend a few minutes (yeah, right - he said much later - a `few minutes'.
Hah) identifying and labelling all my Ethernet cables. Hmm. Tea. Yes.

<phew>

Cables are now labelled. Some of them turned out to be quite hard to
pull out of the places they'd been run.

The cable that had been going from the 10/100 switch to the printer was
a cross-over cable. It used to work fine.

- next, is your switch a managed device?

<cough> As I said at the top of my initial post:

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

Except that they're both switches (silly boy that I am).

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.

They're both unmanaged, and AFAICT, neither has a dedicated uplink port.
The blurb for the gigabit switch (Netgear GS605) says:

`Auto uplink technology adjusts for either of the two common kinds of
cables; and with its embedded plug and play technology, you simply turn
it on and it works'.

The blurb for the Netgear FS608 v2 8 port 10/100 <cough> *switch* says:

`[snip description of straight through and cross-over cables]

With the Autouplink feature, you don't have to worry about which [sort
of cable] you use. Each port on the FS608v2 switch automatically
configures itself correctly when you plug in a device's cable'

I had the 10/100 switch and the gigabit switch connected with a
straight-through cable yesterday and they `just worked'.

I've checked the paper docs that came with the G4 and G5: nothing there
about where or not the ports are auto-sensing. I've checked the printer
manual (on CD) - again, nothing about whether its Ethernet port is
autosensing (in the case of the printer, I'd bet it's not).

Righto - I've found developer docs for the 2003 MDD 1.25GHz 2G4, which
say:

`The PowerMac G4 computer has a built-in Ethernet port that supports
10Base-T, 100Base-T, and 1000Base-T Gigabit transfer rates. In
operation, the actual speed of the link is auto-negotiated between the
computer's PHY device and the hub, switch, or router to which it is
connected. The Ethernet port is auto-sensing and self-configuring to
allow connection via either a cross-over or straight-through cable.

Both CAT 5 unshielded twisted pair (UTP) and shielded twisted pair (STP)
cables work with the Ethernet port. An STP cable is recommended for
noisy environments or run of greater than 100 meters.

Note: When connecting a PowerMac G4 computer directly to another
computer without using an Ethernet hub, a crossover cable is not
required; circuits in the PHY detect the type of connection and switch
the signal configuration as required.'

I've got a developer pdf for the older twin G5 Macs, which says:

`Note: When connecting a Power Mac G5 computer directly to another
computer without using an Ethernet hub, a crossover cable is not
required; circuits in the PHY detect the type of connection and switch
the signal configuration as required.'

I think I'll `just assume' that the new quad G5 I've got here has the
same - how about it?

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.

Righto - thanks.

[snip]

So: the current state of play is that I've got the G4, G5, and printer
all plugged into the gigabit switch. They are all plugged in using
straight through cables (checked).

The gigabit switch is showing a green light on the ports used for the G4
and the G5. It's showing a yellow light on the port used for the
printer. I assume that green means 1000 Mbit/s and yellow means 100
Mbit/s (the docs do not say).

The G4 and G5 are happily being file servers for each other as I type -
no trouble there.

The printer has a green LED lit up underneath its Ethernet socket, into
which the cable is plugged. There is another LED just above the
printer's Ethernet socket, which is not lit. The manual says that one
means 10Mbit/s and the other means 100Mbit/s, but doesn't tell you which
and there's nothing on the back of the printer to tell you either. The
LED was not lit before I plugged the cable in. When I connected the
printer to the gigabit switch, I got the yellow light turn up on the
appropriate port on the gigabit switch.

Neither the G5 nor the G4 can print to the LJ1320n. The `utility' (url
to point a Web browser at the printer's internal Web server) results in
the Web browser being unable to find the Web page it's pointed at.

On the G4, I tried deleting the LJ 1320n printer, and then adding it
(Printer Utility). I hit `add', and looked at Rendezvous (this is
10.3.9, after all). Nothing showed up. Bonjour browser running on the
G4 showed no sign of the printer.

I've switched the printer off, left it for a minute or so, and switched
it back on again. When the printer was off, the yellow light for `it's
port on the gigabit switch went out, as did all the lights on the
printer (it's got a real off switch). When I turned it back on, there
was a short delay and the various lights came on as before.

Bonjour browser (re-launched) still couldn't see the printer, and nor
could Printer Utility (add printer, Rendezvous).

I then spent something like an hour reading the various bits of
documentation on my printer and *eventually*, after looking at an email
I'd received from HP when I was first trying to set the thing up,
followed a link to a page on HP's Web site that explained how to sort
this steaming load of bollocks out.

Can you believe that if you look in the obvious place and follow the HP
instructions on printing out a network configuration page for the HP
1320n, you get a guaranteed paper jam? If you look in a less obvious
place, you get *different* instructions which work, but... Argh.

Can I scream, please?

So, I got it working all via the gigabit switch. Now to try the
topography I'd rather use (why? Well, there's an `issue' regarding
cables reaching where they need to go conveniently, and all that - the
printer data cable has to go the long way round this room, and I also
need to get a cable downstairs through a hole in the floor/ceiling and
if you look at the routing - well... Oh yeah, and I might be sticking a
hole in the wall to put a cable into the bedroom - my other half banned
computers in the bedroom, but since she's the one who keeps bringing the
iBook to bed, and she's the one who'd find it handy to be able to print
and access the `big' Macs as file servers - well, I might as well.)

Right. So what I've done is connected the gigabit switch to the 10/100
switch using a straight-through patch cable (exactly as not recommended,
but, oh don't ask, available cables an' all that and given that both
switches are from the same firm and claim to be able to `just work'
whatever the cable - well, the `same firm' bit should give it a decent
chance of working, surely?). I then connected the printer to the 10/100
switch.

And it works.

I must have had gremlins. Now what I need to do is unplug everything
and put it all back together with sensible cable routing. Blue and
yellow wires all over the floor might be pretty, but they're a bit in
the way. I think I might leave that until I've had Rentokill round to
deal with the gremlins.

Cheers for the explanations and all that - I wish I knew what it was
that was wrong. But regardless of that: you've taught me some dead
useful stuff which I have saved for future reference.

Ta muchly,
Rowland.

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