Ethernet link weirdness

A friend's Asus laptop connects fine to my own home router but fails to
connect to her ADSL modem using the very same ethernet cable. The "LNK"
indicator light on her modem doesn't light at all, whereas my Apple
laptop connects fine to her modem using the same cable and the LNK light
illuminates immediately.

I wondered if this was an ethernet link speed and duplex
auto-negotiation problem, so I set both the ADSL modem and the Asus
laptop to use 10 half duplex, but the problem persists. In fact
desperation lead me to try several different settings for the link all
with the same disappointing result.

I'm baffled. Can anyone here suggest *any* reason why the Asus laptop
and the ADSL modem fail to establish ethernet link, while the same
laptop works fine with the same cable elsewhere, and another laptop
works fine with the same cable and ADSL modem?

PS. You may have seen this posting separately in the TCP/IP group.
Sorry, I forgot to crosspost.

--
James Taylor

Did you try a cross-over cable?

"James Taylor" <(E-Mail Removed)> wrote in message
news:1hr9f2i.1cfu9pk17q6mlwN%(E-Mail Removed). co.uk.invalid...
>A friend's Asus laptop connects fine to my own home router but fails to
> connect to her ADSL modem using the very same ethernet cable. The "LNK"
> indicator light on her modem doesn't light at all, whereas my Apple
> laptop connects fine to her modem using the same cable and the LNK light
> illuminates immediately.
>
> I wondered if this was an ethernet link speed and duplex
> auto-negotiation problem, so I set both the ADSL modem and the Asus
> laptop to use 10 half duplex, but the problem persists. In fact
> desperation lead me to try several different settings for the link all
> with the same disappointing result.
>
> I'm baffled. Can anyone here suggest *any* reason why the Asus laptop
> and the ADSL modem fail to establish ethernet link, while the same
> laptop works fine with the same cable elsewhere, and another laptop
> works fine with the same cable and ADSL modem?
>
> PS. You may have seen this posting separately in the TCP/IP group.
> Sorry, I forgot to crosspost.
>
> --
> James Taylor



--
Posted via a free Usenet account from http://www.teranews.com

Drake <(E-Mail Removed)> wrote:

> James Taylor wrote:
>
> > I'm baffled. Can anyone here suggest *any* reason why the Asus laptop
> > and the ADSL modem fail to establish ethernet link, while the same
> > laptop works fine with the same cable elsewhere, and another laptop
> > works fine with the same cable and ADSL modem?
>
> Did you try a cross-over cable?

I didn't because I don't have one easily at hand, but that's an
excellent idea, thanks. I may just have to make one up myself.

In order for the crossover-ness to be an issue, both the laptop and the
ADSL modem must be unable to do MDI/MDIX auto-sensing, and the ADSL
modem must expect to be connected to a hub or through a crossover cable
(neither of which is mentioned in the manual). So I am somewhat
doubtful, but at this stage anything's worth a try. ;-)

Thanks.
--
James Taylor

In article <1hr9f2i.1cfu9pk17q6mlwN%(E-Mail Removed) k.invalid>
James Taylor <(E-Mail Removed)> wrote:
> A friend's Asus laptop connects fine to my own home router but fails to
> connect to her ADSL modem using the very same ethernet cable. The "LNK"
> indicator light on her modem doesn't light at all, whereas my Apple
> laptop connects fine to her modem using the same cable and the LNK light
> illuminates immediately.
>
Is it a crossover cable?

In article <1hra2ky.1aro8andrd0rbN%(E-Mail Removed) .invalid>
James Taylor <(E-Mail Removed)> wrote:
> Drake <(E-Mail Removed)> wrote:
>
> > James Taylor wrote:
> >
> > > I'm baffled. Can anyone here suggest *any* reason why the Asus laptop
> > > and the ADSL modem fail to establish ethernet link, while the same
> > > laptop works fine with the same cable elsewhere, and another laptop
> > > works fine with the same cable and ADSL modem?
> >
> > Did you try a cross-over cable?
>
> I didn't because I don't have one easily at hand, but that's an
> excellent idea, thanks. I may just have to make one up myself.
>
Are you sure the cable you have isn't a crossover? I think that would
be more likely to cause the symptoms you are experiencing.

Rob Morley <(E-Mail Removed)> wrote:

> Are you sure the cable you have isn't a crossover?

Yes, very sure. It's a standard patch cable, purchased as such.

> I think that would be more likely to cause the symptoms
> you are experiencing.

Agreed. Weird isn't it.

--
James Taylor

Rob Morley <(E-Mail Removed)> wrote:

> James Taylor wrote:
>
> > Drake <(E-Mail Removed)> wrote:
> >
> > > Did you try a cross-over cable?
> >
> > I didn't because I don't have one easily at hand, but that's an
> > excellent idea, thanks. I may just have to make one up myself.
>
> Are you sure the cable you have isn't a crossover? I think that would
> be more likely to cause the symptoms you are experiencing.

Ok, now that I've tried a crossover cable I discover that it works fine.
The ADSL modem actually *required* a crossover cable and yet there was
no mention of this odd requirement anywhere in the user guide. The only
sensible reason for this that I can think of is that the manufacturer
expected the ethernet output from the ADSL modem to be connected via a
straight through patch cable to a hub and not directly to a computer.
Even so, this oddness really should have been mentioned in the user
guide. Oh well.

Thanks for helping.

--
James Taylor

In article <1hrc9ed.1fhpsbay0u3m1N%(E-Mail Removed) .invalid>
James Taylor <(E-Mail Removed)> wrote:
> Rob Morley <(E-Mail Removed)> wrote:
>
> > James Taylor wrote:
> >
> > > Drake <(E-Mail Removed)> wrote:
> > >
> > > > Did you try a cross-over cable?
> > >
> > > I didn't because I don't have one easily at hand, but that's an
> > > excellent idea, thanks. I may just have to make one up myself.
> >
> > Are you sure the cable you have isn't a crossover? I think that would
> > be more likely to cause the symptoms you are experiencing.
>
> Ok, now that I've tried a crossover cable I discover that it works fine.
> The ADSL modem actually *required* a crossover cable and yet there was
> no mention of this odd requirement anywhere in the user guide.

Very strange.

> The only
> sensible reason for this that I can think of is that the manufacturer
> expected the ethernet output from the ADSL modem to be connected via a
> straight through patch cable to a hub and not directly to a computer.

But hubs usually have either a dedicated uplink port or one that can be
crossed with a switch.

> Even so, this oddness really should have been mentioned in the user
> guide. Oh well.
>
What's the modem, in case anyone Googles with the same problem?

Rob Morley wrote:

> James Taylor wrote:
>
> > Ok, now that I've tried a crossover cable I discover that it
> > works fine. The ADSL modem actually *required* a crossover
> > cable and yet there was no mention of this odd requirement
> > anywhere in the user guide.
>
> Very strange.
>
> > The only sensible reason for this that I can think of is that
> > the manufacturer expected the ethernet output from the
> > ADSL modem to be connected via a straight through
> > patch cable to a hub and not directly to a computer.
>
> But hubs usually have either a dedicated uplink port or one that
> can be crossed with a switch.

Yes, quite. However, I've since discovered that the previous owner of
the ADSL modem had it working in exactly this way; by connecting it to
one of the normal ports of a hub leaving the uplink port unused.

> > Even so, this oddness really should have been mentioned in
> > the user guide. Oh well.
>
> What's the modem, in case anyone Googles with the same problem?

It's a Planet ADE-3100 A (version 2) as you might still find here:

<http://www.planet.com.tw/product/pro...d=185&menu_id=
12>

User guide here:

<ftp://ftp1.planet.com.tw/ADSL/ADE-3100/EM-ADE3100v2.zip>

If you look in that FTP directory you'll also find the user guide for
the first version of this ADSL modem and on page 5 it even says to use
standard LAN cables. The version 2 manual doesn't mention it at all.
Quite why it requires a crossover cable I simply cannot fathom.

--
James Taylor