wire question on Cat5 or Cat5e cables

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Good Day,

I was handed a network that I am responsible for.  I do not have a lot of
experience with cabling which is why I am coming here for some advise.

I have ran some cable, eight runs which is connected to a Cat5e Patch Panel.
I later tested those runs with a tester and wiremap and it came out perfect.
All pares match up.

This is where my problem comes in, during some maintenance work I found that
I had some problems identifying some cables (I did not run these cables and
they are connect to a Cat5 patch panel, and it seems that we have a mix of
Cat5e and Cat5 cables).  The tools that I have also have some attachments
that I can connect to jacks and using my main tool allows me to identify
what office it is.  Such as office 1 - 8 (note office 4 is also my wiremap
tester) thus I can put these devices into jacks and go to the patch panel
and make sure that they are linked to the proper location.  I had four of
these connections that I wanted to test out that leads to our computer room.
I plugged in 1 -4 and started tested.  three and four came out fine and I
wrote down the port numbers on the wall plate but on the other two I started
getting some funny errors.  It seemed that both was showing as office1 and I
was not getting office 2. So I switched to office three and it also showed
up wrong.  This allowed me to rule out bad hardware.  I then took number 4
(which I have used a lot so I know it works) and hooked that up and it came
out wrong.  I switched over to wiremap testing and it showed that I had
shorts in the cable.  I am not sure which lines were shorted and I can
retest if needed to find out and write back here.

So now to my question, after reading stuff on cabling I see that only the
following lines are used 1,2,3, and 6 and I have to assume that they have to
be connected alike at both ends.
So if lines 4,5,7 and 8 were crossed with each other would that cause
problems.  The cable is working from what I see

What type of problems could I have?
If 4,5,7 and 8 were crossed with each other would the cable still work at
all?
If these lines were crossed with 1,2,3 and 6 would the cable work at all?

Thanks for the help
Adam Raff




Re: wire question on Cat5 or Cat5e cables


Hi Adam,
It was a long message, so I post on top.

It looks like only two pairs in your cables were terminated, clearly for
Ethernet application only. The rest of the pairs is going to be used if
you change the cable's application. For example an analog phone would have
to use pair #1 (conductors 4 and 5, missing in your test), and in you case
would not work. Also, the additional pairs are going to be required if you
are trying to implement Power over Ethernet, especially high-power version
of it or if you are trying to go Gigabit Ethernet. So, in your case those
two applications are out of reach.
With a standard 100BASE-TX equipment it would not really matter if the
"missing" conductors are shorted or crossed somehow: they are usually ALL
connected to the ground plane of the Ethernet switch/hub.

--
Dmitri Abaimov, RCDD
http://www.cabling-design.com
Cabling Forum, color codes, pinouts and other useful resources for
premises cabling users and pros
http://www.cabling-design.com/homecabling
Residential Cabling Guide
-------------------------------------
Adam Raff wrote:


> Good Day,

> I was handed a network that I am responsible for.  I do not have a lot
> of
> experience with cabling which is why I am coming here for some advise.

> I have ran some cable, eight runs which is connected to a Cat5e Patch
> Panel.
> I later tested those runs with a tester and wiremap and it came out
> perfect.
> All pares match up.

> This is where my problem comes in, during some maintenance work I found
> that
> I had some problems identifying some cables (I did not run these cables
> and
> they are connect to a Cat5 patch panel, and it seems that we have a mix
> of
> Cat5e and Cat5 cables).  The tools that I have also have some
> attachments
> that I can connect to jacks and using my main tool allows me to
> identify
> what office it is.  Such as office 1 - 8 (note office 4 is also my
> wiremap
> tester) thus I can put these devices into jacks and go to the patch
> panel
> and make sure that they are linked to the proper location.  I had four
> of
> these connections that I wanted to test out that leads to our computer
> room.
> I plugged in 1 -4 and started tested.  three and four came out fine and
> I
> wrote down the port numbers on the wall plate but on the other two I
> started
> getting some funny errors.  It seemed that both was showing as office1
> and I
> was not getting office 2. So I switched to office three and it also
> showed
> up wrong.  This allowed me to rule out bad hardware.  I then took
> number 4
> (which I have used a lot so I know it works) and hooked that up and it
> came
> out wrong.  I switched over to wiremap testing and it showed that I had
> shorts in the cable.  I am not sure which lines were shorted and I can
> retest if needed to find out and write back here.

> So now to my question, after reading stuff on cabling I see that only
> the
> following lines are used 1,2,3, and 6 and I have to assume that they
> have to
> be connected alike at both ends.
> So if lines 4,5,7 and 8 were crossed with each other would that cause
> problems.  The cable is working from what I see

> What type of problems could I have?
> If 4,5,7 and 8 were crossed with each other would the cable still work
> at
> all?
> If these lines were crossed with 1,2,3 and 6 would the cable work at
> all?

> Thanks for the help
> Adam Raff










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Re: wire question on Cat5 or Cat5e cables




[sbip]

> With a standard 100BASE-TX equipment it would not really matter if the
> "missing" conductors are shorted or crossed somehow: they are usually
ALL
> connected to the ground plane of the Ethernet switch/hub.

I checked a 3Com NIC, and I found that the unused pairs were connected
to ground as you said.  The problem I see with this is that the newer
Crisco switches may have POE, power over ethernet, for a VoIP phone,
etc.  If that is turned on, the shorted pairs could draw excessive
current.

> --
> Dmitri Abaimov, RCDD
[snip]




Re: wire question on Cat5 or Cat5e cables


Watson A.Name - "Watt Sun, the Dark Remover" wrote:

> I checked a 3Com NIC, and I found that the unused pairs were connected
> to ground as you said.  The problem I see with this is that the newer
> Crisco switches may have POE, power over ethernet, for a VoIP phone,
> etc.  If that is turned on, the shorted pairs could draw excessive
> current.

The PoE specs allow for that possibility.



Re: wire question on Cat5 or Cat5e cables



> Watson A.Name - "Watt Sun, the Dark Remover" wrote:
>
> > I checked a 3Com NIC, and I found that the unused pairs were
connected
> > to ground as you said. The problem I see with this is that the newer
> > Crisco switches may have POE, power over ethernet, for a VoIP phone,
> > etc. If that is turned on, the shorted pairs could draw excessive
> > current.
>
> The PoE specs allow for that possibility.

That's reassuring to know.

Right now, we are using WAPs that have an injector that plugs into a
wall wart, then into the wall outlet.  I would guess they have some form
of protection, but I don't know.  They're mostly Crisco, I believe.





Re: wire question on Cat5 or Cat5e cables


James Knott wrote:
> Watson A.Name - "Watt Sun, the Dark Remover" wrote:
>
>
>>I checked a 3Com NIC, and I found that the unused pairs were connected
>>to ground as you said.  The problem I see with this is that the newer
>>Crisco switches may have POE, power over ethernet, for a VoIP phone,
>>etc.  If that is turned on, the shorted pairs could draw excessive
>>current.
>
>
> The PoE specs allow for that possibility.
>
But as far as I remember, the one port Cisco power injectors has no
protection and will just feed power.

Go for real PoE midspan devices that follov the PoE standard, then you
are safe.

--
The Cabling Guy
I only express my own personal opinion on Usenet.


Re: wire question on Cat5 or Cat5e cables


Watson A.Name - "Watt Sun, th wrote:

> "Dmitri(Cabling-Design.com)"

> [sbip]

>> With a standard 100BASE-TX equipment it would not really matter if
>> the
>> "missing" conductors are shorted or crossed somehow:
>> they are usually
> ALL
>> connected to the ground plane of the Ethernet switch/hub.

> I checked a 3Com NIC, and I found that the unused pairs were connected
> to ground as you said.  The problem I see with this is that the newer
> Crisco switches may have POE, power over ethernet, for a VoIP phone,
> etc.  If that is turned on, the shorted pairs could draw excessive
> current.

>> --
>> Dmitri Abaimov, RCDD
>> [snip]

It is a part of the IEEE 802.3af protocol to poll the equipment on the
other end to see if there is a short. However, it is an issue with DIY
Power-over-Ethernet. I personally fried quite a few power supplies few
years ago doing some DIY Power-over-Ethernet for early IP cameras we
installed.

--
Dmitri Abaimov, RCDD
http://www.cabling-design.com
Cabling Forum, color codes, pinouts and other useful resources for
premises cabling users and pros
http://www.cabling-design.com/homecabling
Residential Cabling Guide
-------------------------------------








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Re: wire question on Cat5 or Cat5e cables



> Watson A.Name - "Watt Sun, th wrote:
>
> > "Dmitri(Cabling-Design.com)"
>
> > [sbip]
>
> >> With a standard 100BASE-TX equipment it would not really matter if
> >> the
> >> "missing" conductors are shorted or crossed somehow:
> >> they are usually
> > ALL
> >> connected to the ground plane of the Ethernet switch/hub.
>
> > I checked a 3Com NIC, and I found that the unused pairs were
connected
> > to ground as you said.  The problem I see with this is that the
newer
> > Crisco switches may have POE, power over ethernet, for a VoIP phone,
> > etc.  If that is turned on, the shorted pairs could draw excessive
> > current.
>
> >> --
> >> Dmitri Abaimov, RCDD
> >> [snip]
>
> It is a part of the IEEE 802.3af protocol to poll the equipment on the
> other end to see if there is a short. However, it is an issue with DIY
> Power-over-Ethernet. I personally fried quite a few power supplies few
> years ago doing some DIY Power-over-Ethernet for early IP cameras we
> installed.

We use a digital PBX system that powers the phones over the single pair.
Each port has a PTC (positive tempco) device made by Murata that is in
series with the 48VDC line.  If there's a short on the 66 block (easy to
do) the blue spark alarms the tech, but the PTC gets hot real quick and
reduces the current from over a hundred mA to just a dozen or less.
It'll stay that way until the short is removed.

You ought to see the tech's eyes light up when he sees that fat blue
spark!  "WHOA!"  What was that?!?!"


> --
> Dmitri Abaimov, RCDD




Re: wire question on Cat5 or Cat5e cables



>
> [sbip]
>
> > With a standard 100BASE-TX equipment it would not really matter if the
> > "missing" conductors are shorted or crossed somehow: they are usually
> ALL
> > connected to the ground plane of the Ethernet switch/hub.
>
> I checked a 3Com NIC, and I found that the unused pairs were connected
> to ground as you said.  

The unused pairs on Etherner card could be, depending on the card
wired on one of the following ways:
1. left floating freely (not connected to anything)
2. free wired wired toghether and connected to ground
   (maybe though coupling capacitor)
3. wires are terminated together through Bob Smith Termination
   (several resistors and then through capacitor to card ground).

Options 1 and 3 seem to be the most common ways this has been done.
This is based on looking at the Ethernet designd on Internet and
looking at some Ethernet equipment I have opened (hubs, switches,
Ethernet cards etc..)

> The problem I see with this is that the newer
> Crisco switches may have POE, power over ethernet, for a VoIP phone,
> etc.  If that is turned on, the shorted pairs could draw excessive
> current.

The current POE standard (IEEE 802.3af) says that the equioment
that feed power to the Ethernet wiring must first check that it
is safe ty feed the power to the wiring. There is a specific
identifiaction  protocol that identified that there is equipment
on the other end of the cable that is designed to take standard POE
power and the protocol even identifies some product features
(what is the power rating of those equipment).
The protocol is such that that it really needs to be a POE
supporting equipment on the cable, before the power supply
will be turned on. And there is also over current protection
if short circuit happens afterwards.
Also earlier pre standard commercial POE impementations
(for example from Cisco and PowerDsine) to my knowledge
has some form of identification system to make sure
that power is not fed to places it should not be fed.

The fact that the normally unused pair could be
connected differently on different Ethernet equipment
it is an issue with DIY Power-over-Ethernet that just
simply feed the power to those free wires.
Depending on the connection you could get a fried
power supply or some fried Bob Smith Termination resistors
on Ethernet card. In any case the power supply for
this kind of tricks should be always so energy limited
(either built in current limit or some fuses or similar)
that short circuit on the wiring does not cause
more current to flow on the wiring that it can safely handle.
For example at equipment buit according POE standard
(IEEE 802.3af) power supplying hub cutoff current limit is
typically around 350mA.

Some more information on POE can be found at
http://www.epanorama.net/links/tele_lan.html#poe



--
Tomi Engdahl (http://www.iki.fi/then /)
Take a look at my electronics web links and documents at
http://www.epanorama.net /


Re: wire question on Cat5 or Cat5e cables



> "Watson A.Name - "Watt Sun, the Dark Remover""
>
> > "Dmitri(Cabling-Design.com)"
> >
> > [sbip]
> >
> > > With a standard 100BASE-TX equipment it would not really matter if
the
> > > "missing" conductors are shorted or crossed somehow: they are
usually
> > ALL
> > > connected to the ground plane of the Ethernet switch/hub.
> >
> > I checked a 3Com NIC, and I found that the unused pairs were
connected
> > to ground as you said.
>
> The unused pairs on Etherner card could be, depending on the card
> wired on one of the following ways:
> 1. left floating freely (not connected to anything)
> 2. free wired wired toghether and connected to ground
>    (maybe though coupling capacitor)
> 3. wires are terminated together through Bob Smith Termination
>    (several resistors and then through capacitor to card ground).
>
> Options 1 and 3 seem to be the most common ways this has been done.
> This is based on looking at the Ethernet designd on Internet and
> looking at some Ethernet equipment I have opened (hubs, switches,
> Ethernet cards etc..)
>
> > The problem I see with this is that the newer
> > Crisco switches may have POE, power over ethernet, for a VoIP phone,
> > etc.  If that is turned on, the shorted pairs could draw excessive
> > current.
>
> The current POE standard (IEEE 802.3af) says that the equioment
> that feed power to the Ethernet wiring must first check that it
> is safe ty feed the power to the wiring. There is a specific
> identifiaction  protocol that identified that there is equipment
> on the other end of the cable that is designed to take standard POE
> power and the protocol even identifies some product features
> (what is the power rating of those equipment).
> The protocol is such that that it really needs to be a POE
> supporting equipment on the cable, before the power supply
> will be turned on. And there is also over current protection
> if short circuit happens afterwards.
> Also earlier pre standard commercial POE impementations
> (for example from Cisco and PowerDsine) to my knowledge
> has some form of identification system to make sure
> that power is not fed to places it should not be fed.
>
> The fact that the normally unused pair could be
> connected differently on different Ethernet equipment
> it is an issue with DIY Power-over-Ethernet that just
> simply feed the power to those free wires.
> Depending on the connection you could get a fried
> power supply or some fried Bob Smith Termination resistors
> on Ethernet card. In any case the power supply for
> this kind of tricks should be always so energy limited
> (either built in current limit or some fuses or similar)
> that short circuit on the wiring does not cause
> more current to flow on the wiring that it can safely handle.
> For example at equipment buit according POE standard
> (IEEE 802.3af) power supplying hub cutoff current limit is
> typically around 350mA.
>
> Some more information on POE can be found at
> http://www.epanorama.net/links/tele_lan.html#poe

Thank you very much for the good info.

However I don't agree with ths following statement:  "When
power-over-Ethernet technology becomes widespread, corporations and
businesses will see at least one set of wiring hassles disappear or
reduced considerably."

The problem is that the use of one pair for power makes it impossible to
use that cable for 1000BT.  Since most PCs are now coming with GB NICs,
and switches will be, too, this means that any cable used for POE will
not allow "full speed", and hencs another cat5 cable will have to be
installed.  PFFFT! There goes your cable minimization!  You now have two
cables.  :-P


> --
> Tomi Engdahl (http://www.iki.fi/then /)
> Take a look at my electronics web links and documents at
> http://www.epanorama.net /




Re: wire question on Cat5 or Cat5e cables


Watson A.Name - "Watt Sun, the Dark Remover" wrote:
>
snip

>>
>>Some more information on POE can be found at
>>http://www.epanorama.net/links/tele_lan.html#poe
>
> Thank you very much for the good info.
>
> However I don't agree with ths following statement:  "When
> power-over-Ethernet technology becomes widespread, corporations and
> businesses will see at least one set of wiring hassles disappear or
> reduced considerably."
>
I fully agree and think that PoE will get bigger impact than many think.

> The problem is that the use of one pair for power

No, it uses 2 pairs. One pair for positive and another for negative.

> makes it impossible to
> use that cable for 1000BT.  

No, the PoE standard has 2 options; to use Spare pairs or phantom power.
For 1000BASE-T phantom power will be used.
You will soon see Mid span devices for 1000BASE-T and wireless AP´s with
1G NIC.
All clients shall accept both power options to comply with the PoE standard.

> Since most PCs are now coming with GB NICs,
> and switches will be, too, this means that any cable used for POE will
> not allow "full speed", and hencs another cat5 cable will have to be
> installed.  PFFFT! There goes your cable minimization!  You now have two
> cables.  :-P
>
Read and learn :-)
www.ieee.org

--
The Cabling Guy
I only express my own personal opinion on Usenet.


Re: wire question on Cat5 or Cat5e cables



> Watson A.Name - "Watt Sun, the Dark Remover" wrote:
> >
> snip
>
> >>
> >>Some more information on POE can be found at
> >>http://www.epanorama.net/links/tele_lan.html#poe
> >
> > Thank you very much for the good info.
> >
> > However I don't agree with ths following statement:  "When
> > power-over-Ethernet technology becomes widespread, corporations and
> > businesses will see at least one set of wiring hassles disappear or
> > reduced considerably."
> >
> I fully agree and think that PoE will get bigger impact than many
think.
>
> > The problem is that the use of one pair for power
>
> No, it uses 2 pairs. One pair for positive and another for negative.
>
> > makes it impossible to
> > use that cable for 1000BT.
>
> No, the PoE standard has 2 options; to use Spare pairs or phantom
power.

Yeah.  The only one I've seen installed is the spare pair affair, in
which case what I said is true.  If the phantom method is used, then the
remaining two pairs should be useable.  The phantom method requires more
transformers with center taps, so it's possible that they are trying to
save money and just use the spare pair.


> For 1000BASE-T phantom power will be used.
> You will soon see Mid span devices for 1000BASE-T and wireless AP´s
with
> 1G NIC.
> All clients shall accept both power options to comply with the PoE
standard.
>
> > Since most PCs are now coming with GB NICs,
> > and switches will be, too, this means that any cable used for POE
will
> > not allow "full speed", and hencs another cat5 cable will have to be
> > installed.  PFFFT! There goes your cable minimization!  You now have
two
> > cables.  :-P
> >
> Read and learn :-)
> www.ieee.org
>
> --
> The Cabling Guy
> I only express my own personal opinion on Usenet.




Re: wire question on Cat5 or Cat5e cables


Watson A.Name - "Watt Sun, the Dark Remover" wrote:

> The problem is that the use of one pair for power makes it impossible to
> use that cable for 1000BT.  Since most PCs are now coming with GB NICs,
> and switches will be, too, this means that any cable used for POE will
> not allow "full speed", and hencs another cat5 cable will have to be
> installed.  PFFFT! There goes your cable minimization!  You now have two
> cables.  :-P

Not necessarily.  It's entirely possible to send both DC and signal over the
same wires.  It's been done for decades, in the communications industry.
Twisted pair ethernet uses transformers to connect the cables to the NIC.
The power can be inserted on the line side of the transformer, without any
effect on the operation of the NIC.



Re: wire question on Cat5 or Cat5e cables


Adam,
  It sounds to me like these guys are going to deep into what you
really need to do. If my understanding is correct, you only have a few
cables that are not passing. I would reterminate the cables on both
ends so that you know they are correct. After reading the other
replies, I don't think you need to get into the "deep end of the
electronics". The cable should be fine, just reterminate.



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