Troubleshooting router

On 11/29/2011 9:06 AM, Kurt Ullman wrote:
> In article<(E-Mail Removed)>,
> Irwell<(E-Mail Removed)> wrote:
>
>> On Tue, 29 Nov 2011 06:32:15 -0500, Kurt Ullman wrote:
>>
>>> In article<(E-Mail Removed) >,
>>> Jeff Liebermann<(E-Mail Removed)> wrote:
>>>
>>>
>>>>
>>>> Power supply failure due to bulging caps. I'm guessing you have the
>>>> white or gray Apple airport that looks like a conical mushroom. I
>>>> have 3 of those in a box with similar symptoms. The only difference
>>>> is that the light was flashing for only a few days before it started
>>>> acting weird.
>>>> <http://www.vonwentzel.net/ABS/Repair/index.html>
>>>
>>> I'm wondering if this could be cable failure. While I don't see any
>>> frank fraying, there is a gap between the end of the plug and the start
>>> of the blue coating on the wire. Also I get the same problem when I plug
>>> in my other Airport (the smaller one that looks like a cigarette pack on
>>> steroids).
>>
>> MOre than likely, and a cable substitute is the first step in
>> trouble shooting.
>
> Especially since I just got done swapping out my big router for the
> little one I travel with occassionally with the same outcome.
>
Ethernet cables going south are not unheard of. I wasted quite a bit of
time once due to a bad ethernet cable. I buy the shielded ones mostly
because they tend to be tougher.

On 11/29/2011 9:45 AM, Jeff Liebermann wrote:
> On Tue, 29 Nov 2011 06:32:15 -0500, Kurt Ullman<(E-Mail Removed)>
> wrote:
>
>> I'm wondering if this could be cable failure. While I don't see any
>> frank fraying, there is a gap between the end of the plug and the start
>> of the blue coating on the wire. Also I get the same problem when I plug
>> in my other Airport (the smaller one that looks like a cigarette pack on
>> steroids).
>
> The small one is the Airport Express. The cable you're looking at is
> the ethernet cable. The gap between the connector and the outer
> jacket is not important since it carries no signals. As long as the
> wires at the ends of the ethernet cable are intact and making a
> connection, it should work.
>
> However, as I vaguely recall (and can't check until I get to my
> palatial office today), the flashing yellow light on the Apple
> Mushroom wireless router means that the ethernet cable is wired wrong
> or backwards. You might check your ethernet cables and where they are
> connected.
>
The newer routers have autosensing and can swap on the fly. I assume
there is a standard in the industry where only routers can autosense.

In article <jb3jkb$971$(E-Mail Removed)>, miso <(E-Mail Removed)>
wrote:

> The newer routers have autosensing and can swap on the fly. I assume
> there is a standard in the industry where only routers can autosense.

Nah, Apple's stuff has had that capability for years. My ol' Sawtooth,
for instance, and certainly our newer machines. I can't imagine any NIC
without it.

--

I been warped by the rain, driven by the snow
I'm drunk and dirty, don't you know
But I'm still
Willin Wilbur

On Tue, 29 Nov 2011 13:40:30 -0800, miso <(E-Mail Removed)> wrote:

>Ethernet cables going south are not unheard of. I wasted quite a bit of
>time once due to a bad ethernet cable. I buy the shielded ones mostly
>because they tend to be tougher.

Long shielded cables give me problems. I had shielded running between
two buildings which happened to be on two different grounding systems.
There was only a few millivolts between the grounds, but they had the
power of PG&E between them. There was no pyrotechnics or smoke, but
plenty of odd problems that magically went away when I lifted *ONE*
ground. I had a similar situation with coax cable between buildings
many years ago. This time, the cable got warm, sparks flew, and the
shield eventually fused open (in the most inconvenient place
possible).

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com (E-Mail Removed)
# http://www.LearnByDestroying.com AE6KS

On 11/29/2011 3:50 PM, Jeff Liebermann wrote:
> On Tue, 29 Nov 2011 13:40:30 -0800, miso<(E-Mail Removed)> wrote:
>
>> Ethernet cables going south are not unheard of. I wasted quite a bit of
>> time once due to a bad ethernet cable. I buy the shielded ones mostly
>> because they tend to be tougher.
>
> Long shielded cables give me problems. I had shielded running between
> two buildings which happened to be on two different grounding systems.
> There was only a few millivolts between the grounds, but they had the
> power of PG&E between them. There was no pyrotechnics or smoke, but
> plenty of odd problems that magically went away when I lifted *ONE*
> ground. I had a similar situation with coax cable between buildings
> many years ago. This time, the cable got warm, sparks flew, and the
> shield eventually fused open (in the most inconvenient place
> possible).
>

Interesting. I just use them over short distances. Ethernet uses
transformers, so I assume there is no issue with the unshielded cables.
It would help to know how they use the shield in the overall cable
configuration.

I know for building to building use in corporate installations, they go
fiber just to get around the ground differential. Nowadays for bandwidth
too, but I recall back in the day fiber wasn't all that fast (due to the
interface hardware), they used it for the ground issue. Math Associates
comes to mind. I heard lots of complaints from the IT guys. Looks like
Irwin Math is still kicking:
> http://www.liteway.com/faq/math_associates.htm

I see fiber optic cards in the surplus shops these day, so perhaps the
technology is getting more mainstream.

On Tue, 29 Nov 2011 19:59:54 -0800, miso <(E-Mail Removed)> wrote:

>Ethernet uses
>transformers, so I assume there is no issue with the unshielded cables.
>It would help to know how they use the shield in the overall cable
>configuration.

The shields are connected to the "frame" of the RJ45 jack, which is
connected to the frame ground. The data wires are rated to 1500 volt
isolation from ground. The problem is that the subsequent internal
circuitry is not so well isolated, especially when the box is passing
a bunch of noise and ripple current directly from the power line going
through the box, through the shield, and through the box at the other
end. The length of the cable should have little effect as the common
mode rejection of the data lines will prevent any coupling from the
shield from affecting the data. It's unlikely to find grounds ad
different potentials with short cables. However, with really long
cables, even grounds on the other side of a build may become a
problem.

Incidentally, the way I found one culprit was that someone turned off
the lights in the wiring closet while I was working. When I unpluged
a patch cable, I noticed a small spark. Not a great way to do
troubleshooting but sometimes luck works.



--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com (E-Mail Removed)
# http://www.LearnByDestroying.com AE6KS