Ethernet linked access point appears sensitive to cable length wellbelow specified limits.

Ethernet linked access point appears sensitive to cable length well
below specified limits.

I’m seeking to locate a wireless access point remote from my main
router, a D-Link DI-524 whose wireless function has been turned off. The
wireless access point is being implemented with a nearly identical
D-Link DI-524 wireless router whose DHCP function has been turned off.
The IP address of the second D-Link DI-524 wireless router has been
altered so as not to conflict with the IP address of the first router.
One of the LAN outputs of the first router is connected to one of the
LAN outputs of the second router so that it acts like a switch.

I have tested the above configuration at three locations linked by three
different CAT5 cables.

Location #1 – WORKS fine when linked by commercially constructed 10’
long CAT5 cable.

Location #2 – WORKS fine when linked by home built 40’ long CAT5 cable.

Location #3 – DOES NOT WORK when linked by home built 100’ long CAT5
cable. – Not only is there no communication over the link, but the
lights on both routers do not even indicate a connection. YET, if at
this same location #3, the 100’ long cable is plugged into any one of
several computers, the connection indicator lights come on immediately,
and full normal network access is quickly obtained.

As the cable length is well under the 100 meter (300 feet) maximum
length for Ethernet, at first I thought that maybe the third cable is
somehow wired differently, perhaps as a “Cross over cable” rather than
as a “straight through” cable. I understand that some interfaces can
cross and un-cross a cable automatically as needed. I am uncertain
whether or not the LAN ports of the DI-524 have that feature, but an
examination of all of my cables, both home made and commercially
assembled, and all appear to be wired “straight through.”

I’ve also sought to confirm that the problem is not associated with the
RJ45 connector at the end of the cable. The symptoms are unchanged when
a short (10 foot long) Ethernet extender (female to male) cable is used,
so the connector at the end of the 100’ cable is not disturbed as I
switch between the D-Link DI-524 and my lap-top computer..

Any Suggestions?

I nominate this post as best of the month for well formed question,
good initial troubleshooting, and supplied information.

Let me have coffee, feed the dogs, moves the cows to another pasture,
then I'll look it over.

added cabling & ethernet newsgroups -
Wonder if a small ethernet cable tester has been used to verify proper pairs
?
--

windsurferLA wrote:
> Ethernet linked access point appears sensitive to cable length well
> below specified limits.
>
> I’m seeking to locate a wireless access point remote from my main
> router, a D-Link DI-524 whose wireless function has been turned off.
> The wireless access point is being implemented with a nearly identical
> D-Link DI-524 wireless router whose DHCP function has been turned off.
> The IP address of the second D-Link DI-524 wireless router has been
> altered so as not to conflict with the IP address of the first router.
> One of the LAN outputs of the first router is connected to one of the
> LAN outputs of the second router so that it acts like a switch.
>
> I have tested the above configuration at three locations linked by
> three different CAT5 cables.
>
> Location #1 – WORKS fine when linked by commercially constructed 10’
> long CAT5 cable.
>
> Location #2 – WORKS fine when linked by home built 40’ long CAT5
> cable.
> Location #3 – DOES NOT WORK when linked by home built 100’ long CAT5
> cable. – Not only is there no communication over the link, but the
> lights on both routers do not even indicate a connection. YET, if at
> this same location #3, the 100’ long cable is plugged into any one of
> several computers, the connection indicator lights come on
> immediately, and full normal network access is quickly obtained.
>
> As the cable length is well under the 100 meter (300 feet) maximum
> length for Ethernet, at first I thought that maybe the third cable is
> somehow wired differently, perhaps as a “Cross over cable” rather than
> as a “straight through” cable. I understand that some interfaces can
> cross and un-cross a cable automatically as needed. I am uncertain
> whether or not the LAN ports of the DI-524 have that feature, but an
> examination of all of my cables, both home made and commercially
> assembled, and all appear to be wired “straight through.”
>
> I’ve also sought to confirm that the problem is not associated with
> the RJ45 connector at the end of the cable. The symptoms are
> unchanged when a short (10 foot long) Ethernet extender (female to
> male) cable is used, so the connector at the end of the 100’ cable is
> not disturbed as I switch between the D-Link DI-524 and my lap-top
> computer..
> Any Suggestions?

On Fri, 02 May 2008 20:27:34 -0700, windsurferLA <(E-Mail Removed)>
wrote:

>Ethernet linked access point appears sensitive to cable length well
>below specified limits.

Appearances are often deceiving.

>I’m seeking to locate a wireless access point remote from my main
>router, a D-Link DI-524 whose wireless function has been turned off.

The DI-524 is not the best router on the planet. I think I have about
3 of them in the office, that have been pulled from service due to
range problems. They're also only 802.11b and are therefore slow. If
you don't need the wireless, there are many better routers available
for literally a few dollars.

>The
>wireless access point is being implemented with a nearly identical
>D-Link DI-524 wireless router whose DHCP function has been turned off.

No problem. I use wireless routers as access points all the time.

>The IP address of the second D-Link DI-524 wireless router has been
>altered so as not to conflict with the IP address of the first router.

Good.

>One of the LAN outputs of the first router is connected to one of the
>LAN outputs of the second router so that it acts like a switch.

Can I presume that you used a cross-over ethernet cable between the
LAN ports on the two DI-524 routers?

>I have tested the above configuration at three locations linked by three
>different CAT5 cables.

Commercial CAT5 cables or home made? I recently found an entire
building, where all the CAT5 wiring was to some odd specification,
which was totally useless for ethernet because it effectively split
one of the pairs of wires. I'm currently negotiating on the price of
replacing the connetors and reterminating about 50 wall jacks.

>Location #1 – WORKS fine when linked by commercially constructed 10’
>long CAT5 cable.

OK. That's your sanity check. Commercial cables are usually (not
always) known good. Is this a cross-over ethernet cable? Note that
LAN to LAN port connections must have a cross-over cable unless ONE of
your boxes has autoconfiguring ports. The DI-524 does NOT have port
auto-configuration and the cables must be cross over.

>Location #2 – WORKS fine when linked by home built 40’ long CAT5 cable.
>
>Location #3 – DOES NOT WORK when linked by home built 100’ long CAT5
>cable. – Not only is there no communication over the link, but the
>lights on both routers do not even indicate a connection. YET, if at
>this same location #3, the 100’ long cable is plugged into any one of
>several computers, the connection indicator lights come on immediately,
>and full normal network access is quickly obtained.

Wrong type of cable. It needs to be a cross over ethernet cable.
<http://en.wikipedia.org/wiki/Ethernet_crossover_cable>
I use the gigabit wiring scheme, where all 4 pairs are crossed over.

>As the cable length is well under the 100 meter (300 feet) maximum
>length for Ethernet, at first I thought that maybe the third cable is
>somehow wired differently, perhaps as a “Cross over cable” rather than
>as a “straight through” cable.

You're not adjusting the cable length. What you're doing is switching
cables, some of which are apparently straight through cables.

>I understand that some interfaces can
>cross and un-cross a cable automatically as needed. I am uncertain
>whether or not the LAN ports of the DI-524 have that feature, but an
>examination of all of my cables, both home made and commercially
>assembled, and all appear to be wired “straight through.”

Most commercial cables are straight through. I don't like to stock
two different wiring configurations. What I use is a home made cross
over adapter. It's an RJ-45 wall jack, with a short CAT5 pigtail to
an RJ-45 plug. The jack is wired normally, but the RJ-45 plug is
wired for cross over. When I need a cross over cable, instead of
destroying a perfectly good straight through molded commercial cable,
I use the adapter. I think you can also buy ethernet cross over
adapters on the web somewhere, but I'm too lazy to look.

>I’ve also sought to confirm that the problem is not associated with the
>RJ45 connector at the end of the cable. The symptoms are unchanged when
>a short (10 foot long) Ethernet extender (female to male) cable is used,
>so the connector at the end of the 100’ cable is not disturbed as I
>switch between the D-Link DI-524 and my lap-top computer..

You're NOT changing the cable length. You're changing the cable
wiring.

>Any Suggestions?

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

On Sat, 03 May 2008 09:47:06 -0700, Jeff Liebermann <(E-Mail Removed)>
wrote:

>The DI-524 is not the best router on the planet. I think I have about
>3 of them in the office, that have been pulled from service due to
>range problems. They're also only 802.11b and are therefore slow. If
>you don't need the wireless, there are many better routers available
>for literally a few dollars.

Oops. Memory fault. The DI-524 will do 802.11g speeds. The one's I
retired were DI-514 wireless routers, which are 802.11b only.


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

> windsurferLA wrote:
>> Location #2 ? WORKS fine when linked by home built 40? long
>> CAT5 cable. Location #3 ? DOES NOT WORK when linked by home
>> built 100? long CAT5 cable. ? Not only is there no communication
>> over the link, but the lights on both routers do not even
>> indicate a connection. YET, if at this same location #3, the
>> 100? long cable is plugged into any one of several computers,
>> the connection indicator lights come on immediately, and full
>> normal network access is quickly obtained.

These homebuilt cables, which wiring pattern did you use?
T-568A or -B ? If you don't know what I'm talking about,
it is highly likely you split a pair.

Please do not complain "but the other comp works".
Difference NICs and drivers are more error-tolerant
and have more robust fall-backs.

Electrons may be color blind, but they _do_ know
who their dance [twist] partners are.

-- Robert

On Sat, 03 May 2008 20:22:07 GMT, Robert Redelmeier
<(E-Mail Removed)> wrote:

>These homebuilt cables, which wiring pattern did you use?
>T-568A or -B ? If you don't know what I'm talking about,
>it is highly likely you split a pair.

Huh? Unless he did something really disgusting, like EIA-568A on one
end and EIA-568B on the other, either wiring standard will work. The
color codes are different, but the pairing is identical.

Drivel: I once had some hired help in wiring a medical office. I did
568B while my hired help did 568A wiring. Nothing worked when we were
done. Never ignore the obvious.

>Please do not complain "but the other comp works".
>Difference NICs and drivers are more error-tolerant
>and have more robust fall-backs.

True. I recently demonstrated that I can run 10baseT-HDX (half
duplex) through 2,000 ft of CAT5e (two rolls in series), without any
data degradation. If I had a 3rd roll, I would have added it. The
catch is that it would only work between my Cisco 1900 ethernet
switch, and a desktop with an Intel Pro100 card. It would function to
other devices (several laptops, assorted junk around the office), but
these showed various errors in the switch SNMP logs.

>Electrons may be color blind, but they _do_ know
>who their dance [twist] partners are.

Perhaps a matchmaker would be appropriate?

>-- Robert

See item #6:
<http://www.LearnByDestroying.com/nooze/support.txt>

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

In comp.dcom.cabling Jeff Liebermann <(E-Mail Removed)> wrote in part:
> On Sat, 03 May 2008 20:22:07 GMT, Robert Redelmeier
>>These homebuilt cables, which wiring pattern did you use?
>>T-568A or -B ? If you don't know what I'm talking about,
>>it is highly likely you split a pair.
>
> Huh? Unless he did something really disgusting, like EIA-568A on one
> end and EIA-568B on the other, either wiring standard will work. The
> color codes are different, but the pairing is identical.

Oh yes, fully agreed. But I think it relatively unlikely
the OP would have followed either without some awareness.
I'm testing for that awareness.

The intuitive wiring patterns (SBS and USOC) will split a pair.
All the correct ones are somewhat counter-intuitive.

> Drivel: I once had some hired help in wiring a medical
> office. I did 568B while my hired help did 568A wiring.
> Nothing worked when we were done. Never ignore the obvious.

Easier to notice and fix with jacks.

> True. I recently demonstrated that I can run 10baseT-HDX (half
> duplex) through 2,000 ft of CAT5e (two rolls in series), without any
> data degradation. If I had a 3rd roll, I would have added it. The
> catch is that it would only work between my Cisco 1900 ethernet
> switch, and a desktop with an Intel Pro100 card. It would function to
> other devices (several laptops, assorted junk around the office), but
> these showed various errors in the switch SNMP logs.

Nice data point.

-- Robert

reply at bottom

Robert Redelmeier wrote:
>> windsurferLA wrote:
>>> Location #2 ? WORKS fine when linked by home built 40? long
>>> CAT5 cable. Location #3 ? DOES NOT WORK when linked by home
>>> built 100? long CAT5 cable. ? Not only is there no communication
>>> over the link, but the lights on both routers do not even
>>> indicate a connection. YET, if at this same location #3, the
>>> 100? long cable is plugged into any one of several computers,
>>> the connection indicator lights come on immediately, and full
>>> normal network access is quickly obtained.
>
> These homebuilt cables, which wiring pattern did you use?
> T-568A or -B ? If you don't know what I'm talking about,
> it is highly likely you split a pair.
>
> Please do not complain "but the other comp works".
> Difference NICs and drivers are more error-tolerant
> and have more robust fall-backs.
>
> Electrons may be color blind, but they _do_ know
> who their dance [twist] partners are.
>
> -- Robert
>

Robert ... thanks for the hint.. the likely cause has been identified.

When you asked about T-568A or T-568B, it triggered a memory. I then
recalled that the connectors were not assembled at the same time; one
end was rebuilt because of intermittent connection problems. The
intermittent end had been the very first RJ45 connector that I had ever
assembled. I further recalled being uncertain at the time I was
rebuilding the connector whether to use the "A" or "B" configuration.

Now doubting my wiring skills, I got out my jeweler's eye loop to very
carefully look at both ends to make sure one had not be wired "A" and
the other "B." The result was not what I expected. A careful
examination of the newer end appears to reveal that the blue-white (#5)
and the green white (#3) were inadvertently interchanged at that end and
only that end.

I expect that repairing the cable will solve the problem. WHAT I FIND
SURPRISING is that the cable has worked with so many (guest's) computers
for so long that it was not until the A - B question was raised that I
thought to check the colors of the inner wires - a not so easy a task
for old eyes like mine. Obviously, there is enough cross talk between
the pairs to effect a connection with most, but not all, hardware.

Although I feel rather stupid for not spotting the wiring error earlier,
I never suspected a wiring error would be the problem. When ever I
assemble a connector, I keep a multi-colored wiring chart right in front
of me. Obviously, it was not enough to preclude the error.

Thanks for everyone's help.. Tomorrow, we try a rebuild.

On Sun, 04 May 2008 03:04:43 GMT, Robert Redelmeier
<(E-Mail Removed)> wrote:

>Oh yes, fully agreed. But I think it relatively unlikely
>the OP would have followed either without some awareness.
>I'm testing for that awareness.

I enjoy asking the original questions backwards. In this case, it's
"what would I have to do, to CREATE the problem"? Creative wiring and
connector terminations are the probable culprits as the terminating
equipment is obviously working.

>The intuitive wiring patterns (SBS and USOC) will split a pair.
>All the correct ones are somewhat counter-intuitive.

I'll do the newsgroup(s) a favor and not rant on how Ma Bell, the old
TIA and the EIA created this mess.

>> Drivel: I once had some hired help in wiring a medical
>> office. I did 568B while my hired help did 568A wiring.
>> Nothing worked when we were done. Never ignore the obvious.
>
>Easier to notice and fix with jacks.

At the time (about 1998), if you purchased any manner of pre-wired
ethernet jumpers, you got EIA-568B wiring. Never mind that EIA-568A
is the real standard. Well, my accomplice was working on his BICSI
certification, and they were preaching EIA-568A. Never mind that I
told him that I wanted the color coding to be consistent throughout
the entire building, all of which was EIA-568B. He decided that BICSI
must be correct and was fully prepared to have me (not him)
re-terminate the entire building (about 400 wall jacks) to insure
compliance. I paid him his fee and hired a day worker from the local
lumber yard. He didn't speak much English, but he undid the damage in
amazingly little time, and finished the job in about half the time I
had expected. The cable certifier found two wiring errors out of
perhaps 60 wall jacks. I was going to pay him a bonus, but that was
before I noticed some of my tools had evaporated. Sigh.

>> True. I recently demonstrated that I can run 10baseT-HDX (half
>> duplex) through 2,000 ft of CAT5e (two rolls in series), without any
>> data degradation. If I had a 3rd roll, I would have added it. The
>> catch is that it would only work between my Cisco 1900 ethernet
>> switch, and a desktop with an Intel Pro100 card. It would function to
>> other devices (several laptops, assorted junk around the office), but
>> these showed various errors in the switch SNMP logs.
>
>Nice data point.

Careful here. That's not an endorsement for installing 2,000ft CAT5e
runs. I once calculated the maximum cable length at about 1,200ft for
10baseT-HDX before timing becomes an issue. Why 2,000ft worked is
still a mystery to me. It shouldn't have unless the timing on the
ethernet devices is more relaxed than required. Also, note that I was
using 10baseT-HDX (half-duplex). Full duplex and/or 100baseT will not
work due to collision domain issues and cable near end crosstalk. You
also have to use an ethernet switch. Hubs (repeaters) will not work.

I do have several 900ft runs in service (one of which goes under some
railroad tracks). No problems. I do have a 500ft run that is giving
me problems. I haven't had time to troubleshoot (due access issues),
but am guessing that I have some induced interference from rotating
machinery, transformers, ballasts, or something similar.

As for stretching the technology, I done my part:
1. DSL over barbed wired. 1Mbit/sec SDSL. Distance is about 3,500ft
of barbed wire, with 100ft of CAT5e at each end. However, the
multiple splices tend to be noisy so it was replaced with a wireless
link about 2 years ago.
2. 10base2 (cheapernet) over CATV 75 ohm RG-6/u coax. Distance was
about 1500ft at one location. The other location was a radio station
that was stuffed full of RG-6/u coax runs. Terminated with 50 ohms at
both ends (because 10base2 uses DC levels for busy detection). Only
two transceivers (no taps or T connectors). With such high losses,
the far end reflections just disappear and never become a problem.
3. FTTS (fiber through the sewer). Actually it's drain under the
road that dumps into the river, but it looks much like a sewer. About
800ft. I keep waiting for it to fail as some water propelled rock
cuts the outer jacket, but it's been up for 8 years and shows no
change in fiber attenuation. I've lost two transceivers, but the
fiber is holding it's own.
4. In the miscellaneous category, I've done ethernet through the
sewers (in order to cross the LATA boundaries), ethernet over 25 pair
telco bundles, ethernet over two 117VAC extension cords (I was
desperate), DSL over zip cord, and adapters made primarily from clip
leads. 900MHz data over G-Line. I won't mention any of my other
wireless atrocities.

One of these days, I'll follow the standards and rules, but not this
week.

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