[27217] in resnet
Re: Ethernet ports "burning out"
daemon@ATHENA.MIT.EDU (Joe Roth)
Fri Jan 27 08:18:05 2012
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Date: Fri, 27 Jan 2012 08:17:55 -0500
Reply-To: Resnet Forum <RESNET-L@listserv.nd.edu>
From: Joe Roth <jroth@binghamton.edu>
To: RESNET-L@listserv.nd.edu
In-Reply-To: <086960B2AF09CC458C0AE60BE5D19D48189F793423@ICE-MBX-6.ice.nd.edu>
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Brad,
Did the students ever trade patch cables or ports in the room? It would
seem like a rare coincidence that BOTH students computers would be damaging
ports on your switch at the same time. I would lean more toward one student
PC breaking one of the ports, then them grabbing their roommates patch
cable or moving their patch cable to the other port within the room, tuis
damaging both ports. Have you asked them if they have done this? This may
narrow your search down to just one student machine causing the issue.
How are the phone pairs run into the room (if they exist)? Are they
terminated anywhere near the ethernet runs? i.e. cabling run to a 66 block,
etc.
Have the students in the room been attempting to use any other piece of
equipment with the network other than their two PCs?
On Thu, Jan 26, 2012 at 11:36 PM, Isaac Holmes <iholmes@nd.edu> wrote:
> Your mentioning the location of the jack near the bed reminded me of an
> incident we had a number of years ago with in a dorm room. Being that the
> jack is on one side of the room and the students always seem to want the
> computers on the other side of the room they have 30-50 foot cables strung
> around the room.
>
> This particular room the jack failed repeatedly over move in week. When
> we went to the room to investigate we found the 30' cable strung around the
> floor of the room and when I was pulling it up to inspect it I found the
> cable had ended up under the leg of the metal bed frame. As it turned out
> there was also a short extension cord right next to it. As I went to move
> it the leg of the bed cut through both the network cable and the extension
> cord. Nothing like popping a circuit breaker and turning off power to half
> the floor of the dorm.
>
> After replacing his cable and making sure it no longer was being cut by
> the bed we had no more issues with that room.
>
>
> Isaac Holmes
> Client Engineering Specialist
>
> OIT Distributed Engineering Support
> University of Notre Dame
>
> B036 IT Center
> (574) 631-3254
>
>
>
> -----Original Message-----
> From: Resnet Forum [mailto:RESNET-L@LISTSERV.ND.EDU] On Behalf Of Brad
> Coburn
> Sent: Thursday, January 26, 2012 11:11 PM
> To: RESNET-L@LISTSERV.ND.EDU
> Subject: Re: Ethernet ports "burning out"
>
> Thank you all for your ideas, comments and support.
>
> Facilities replaced the cable this afternoon, tech re-terminated
> everything and confirmed data is flowing, so now we wait.
>
> If the problem recurs, we will separate the connections between two closet
> switches. Not that I want dead ports on two switches, but maybe the
> isolation will be sufficient to show us something.
>
> Next after that will probably be to patch them back into the desktop
> Netgear in the closet. I prefer to keep any equipment locked up and out of
> the hands of the students.
>
> The switches are Extreme Networks, Summit 200-48 (old) and Summit
> X250e-48t (the new one just installed).
>
>
> Let me toss this out there: What does anyone think about (severe) ESD
> being a possibility? It's winter time, humidity is low. The bed is right
> next to the jack. Maybe a large charge developed between PJs and bed
> covers? Like most of us, I get some nasty shocks this time of year. I
> think it's a stretch, but if you're writing a paper while lounging on
> the bed, no power supply connected, and happen to get up or sit down and
> touch that patch cord, or even just the machine, perhaps the UTP
> connection is a good enough drain for a large static build-up? Or
> another way to ask this, is why would this NOT be a serious
> consideration? (Besides about 3500 students in residence who haven't
> have this problem on a regular basis over almost 20 years?) LOL
>
>
> In the meantime, to some of the suggestions and comments:
>
> * Did the ports recover after they were unused for a while, or
> were they blown? (and similar thoughts about enabling/disabling ports)
> --The Extreme SE recommended toggling the port enable. No change. I even
> tried looking in the log to see if maybe the switch detected station
> link up but wasn't able to respond. No dice. The switches that have had
> port problems in the past don't experience "reanimation" (unless someone
> mis-diagnosed the problem and incorrectly tagged the port bad). Very old
> models cascade failure to 4- and 8-port groups when the ASICS finally
> go. Our experience with port failures on switches in other buildings
> (since we didn't always believe that a port could really "fail") is that
> they're toast.
>
> * To the vendor/TAC calls, it's something on the to-do. We have an
> email
> for our SE and he had some off-the-cuff suggestions but nothing
> groundbreaking. We have RMA'd switches with bad ports back, but all they
> do is ship a replacement unit and close the call. We will try to see if
> we can get someone to actually work the problem when things calm down.
>
> * Where did you check pair to ground voltage? In the closet or
> in the room? It sounds as if you have a floating ground in the room,
> but if you checked voltage there, maybe not.
> --Tried to check that. I have a 3M tester used for telco OSP copper
> testing. Looked at tip-ring and tip/ring-ground for each pair, both
> voltage and resistance. Used the TDR function, alone and comparative
> (two pairs simultaneous); nothing apparent. The equipment rooms are
> powered with normal dedicated circuits, maybe two; for these events no
> other switches in the rack are affected.
>
> * Can you isolate the PC and Mac on separate electrical circuits
> to see which one fails again?
> -- Didn't try this one, but it might be impractical. I believe the
> building to be old enough that there's one 20A circuit per room. If not,
> I'm not sure how to sufficiently and clearly explain the idea to them.
> They do have their beds/desks on opposite sides of the room, so that
> might achieve the goal.... Additional discussion around the office on
> the topic of power-supply problems degrade into resignation that if
> power was the problem something worse should be happening that would be
> evident to the students.
>
> * Is it an option to put an in-line circuit breaker on the port
> connections?
> --Definitely an option. I might have something in a back room somewhere,
> otherwise I have a price for a device that might work. I only wish the
> things would present an obvious fault condition; most of the devices
> look like they will only fail obviously for a catastrophic event (e.g.
> lightning).
>
> * Is there a microwave, hair drier, or some other device that
> may induce transients on the line? Maybe one of them has a bad power
> supply.
> -- Quite possible; the room is tight. However the typical room layouts
> that student choose put all the appliances near the jack anyway; the
> CATV port is there and the refridge/micro tower makes a nice TV stand
> (if not terribly sturdy).
>
> * Various comments about cable running past high voltage equipment or
> facilities
> -- There's nothing like that in the hallway ceiling or in the riser
> rooms. We traced the cable through the ceiling. Hoped to find damage
> where the bundles ended up against pipe hangers, but no dice.
>
> -Brad
>
> ___________________________________________________
> You are subscribed to the ResNet-L mailing list.
>
> To subscribe, unsubscribe or search the archives,
> go to http://LISTSERV.ND.EDU/archives/resnet-l.html
> ___________________________________________________
>
> ___________________________________________________
> You are subscribed to the ResNet-L mailing list.
>
> To subscribe, unsubscribe or search the archives,
> go to http://LISTSERV.ND.EDU/archives/resnet-l.html
> ___________________________________________________
>
--
Joe Roth
Networking Group
Binghamton University
Ph. 607-777-7528
Fax 607-777-4009
___________________________________________________
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Brad,<div><br></div><div>Did the students ever trade patch cables or ports =
in the room? It would seem like a rare coincidence that BOTH students compu=
ters would be damaging ports on your switch at the same time. I would lean =
more toward one student PC breaking one of the ports, then them grabbing th=
eir roommates patch cable or moving their patch cable to the other port wit=
hin the room, tuis damaging both ports. Have you asked them if they have do=
ne this? This may narrow your search down to just one student machine causi=
ng the issue.</div>
<div><br></div><div>How are the phone pairs run into the room (if they exis=
t)? Are they terminated anywhere near the ethernet runs? i.e. cabling run t=
o a 66 block, etc.</div><div><br></div><div>Have the students in the room b=
een attempting to use any other piece of equipment with the network other t=
han their two PCs?<br>
<br><div class=3D"gmail_quote">On Thu, Jan 26, 2012 at 11:36 PM, Isaac Holm=
es <span dir=3D"ltr"><<a href=3D"mailto:iholmes@nd.edu">iholmes@nd.edu</=
a>></span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"margin:0=
0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Your mentioning the location of the jack near the bed reminded me of an inc=
ident we had a number of years ago with in a dorm room. =A0Being that the j=
ack is on one side of the room and the students always seem to want the com=
puters on the other side of the room they have 30-50 foot cables strung aro=
und the room.<br>
<br>
This particular room the jack failed repeatedly over move in week. =A0When =
we went to the room to investigate we found the 30' cable strung around=
the floor of the room and when I was pulling it up to inspect it I found t=
he cable had ended up under the leg of the metal bed frame. =A0As it turned=
out there was also a short extension cord right next to it. =A0As I went t=
o move it the leg of the bed cut through both the network cable and the ext=
ension cord. =A0Nothing like popping a circuit breaker and turning off powe=
r to half the floor of the dorm.<br>
<br>
After replacing his cable and making sure it no longer was being cut by the=
bed we had no more issues with that room.<br>
<br>
<br>
Isaac Holmes<br>
Client Engineering Specialist<br>
<br>
OIT Distributed Engineering Support<br>
University of Notre Dame<br>
<br>
B036 IT Center<br>
<a href=3D"tel:%28574%29%20631-3254" value=3D"+15746313254">(574) 631-3254<=
/a><br>
<div class=3D"im HOEnZb"><br>
<br>
<br>
-----Original Message-----<br>
From: Resnet Forum [mailto:<a href=3D"mailto:RESNET-L@LISTSERV.ND.EDU">RESN=
ET-L@LISTSERV.ND.EDU</a>] On Behalf Of Brad Coburn<br>
</div><div class=3D"HOEnZb"><div class=3D"h5">Sent: Thursday, January 26, 2=
012 11:11 PM<br>
To: <a href=3D"mailto:RESNET-L@LISTSERV.ND.EDU">RESNET-L@LISTSERV.ND.EDU</a=
><br>
Subject: Re: Ethernet ports "burning out"<br>
<br>
Thank you all for your ideas, comments and support.<br>
<br>
Facilities replaced the cable this afternoon, tech re-terminated everything=
and confirmed data is flowing, so now we wait.<br>
<br>
If the problem recurs, we will separate the connections between two closet =
switches. Not that I want dead ports on two switches, but maybe the isolati=
on will be sufficient to show us something.<br>
<br>
Next after that will probably be to patch them back into the desktop Netgea=
r in the closet. I prefer to keep any equipment locked up and out of the ha=
nds of the students.<br>
<br>
The switches are Extreme Networks, Summit 200-48 (old) and Summit X250e-48t=
(the new one just installed).<br>
<br>
<br>
Let me toss this out there: What does anyone think about (severe) ESD<br>
being a possibility? It's winter time, humidity is low. The bed is righ=
t<br>
next to the jack. Maybe a large charge developed between PJs and bed<br>
covers? Like most of us, I get some nasty shocks this time of year. I<br>
think it's a stretch, but if you're writing a paper while lounging =
on<br>
the bed, no power supply connected, and happen to get up or sit down and<br=
>
touch that patch cord, or even just the machine, perhaps the UTP<br>
connection is a good enough drain for a large static build-up? Or<br>
another way to ask this, is why would this NOT be a serious<br>
consideration? (Besides about 3500 students in residence who haven't<br=
>
have this problem on a regular basis over almost 20 years?) LOL<br>
<br>
<br>
In the meantime, to some of the suggestions and comments:<br>
<br>
* =A0 =A0 =A0 =A0 Did the ports recover after they were unused for a while,=
or<br>
were they blown? (and similar thoughts about enabling/disabling ports)<br>
--The Extreme SE recommended toggling the port enable. No change. I even<br=
>
tried looking in the log to see if maybe the switch detected station<br>
link up but wasn't able to respond. No dice. The switches that have had=
<br>
port problems in the past don't experience "reanimation" (unl=
ess someone<br>
mis-diagnosed the problem and incorrectly tagged the port bad). Very old<br=
>
models cascade failure to 4- and 8-port groups when the ASICS finally<br>
go. Our experience with port failures on switches in other buildings<br>
(since we didn't always believe that a port could really "fail&quo=
t;) is that<br>
they're toast.<br>
<br>
* =A0 =A0 =A0 To the vendor/TAC calls, it's something on the to-do. We =
have an email<br>
for our SE and he had some off-the-cuff suggestions but nothing<br>
groundbreaking. We have RMA'd switches with bad ports back, but all the=
y<br>
do is ship a replacement unit and close the call. We will try to see if<br>
we can get someone to actually work the problem when things calm down.<br>
<br>
* =A0 =A0 =A0 =A0 Where did you check pair to ground voltage? =A0In the clo=
set or<br>
in the room? =A0It sounds as if you have a floating ground in the room,<br>
but if you checked voltage there, maybe not.<br>
--Tried to check that. I have a 3M tester used for telco OSP copper<br>
testing. Looked at tip-ring and tip/ring-ground for each pair, both<br>
voltage and resistance. Used the TDR function, alone and comparative<br>
(two pairs simultaneous); nothing apparent. =A0The equipment rooms are<br>
powered with normal dedicated circuits, maybe two; for these events no<br>
other switches in the rack are affected.<br>
<br>
* =A0 =A0 =A0 =A0 Can you isolate the PC and Mac on separate electrical cir=
cuits<br>
to see which one fails again?<br>
-- Didn't try this one, but it might be impractical. I believe the<br>
building to be old enough that there's one 20A circuit per room. If not=
,<br>
I'm not sure how to sufficiently and clearly explain the idea to them.<=
br>
They do have their beds/desks on opposite sides of the room, so that<br>
might achieve the goal.... =A0Additional discussion around the office on<br=
>
the topic of power-supply problems degrade into resignation that if<br>
power was the problem something worse should be happening that would be<br>
evident to the students.<br>
<br>
* =A0 =A0 =A0 =A0 Is it an option to put an in-line circuit breaker on the =
port<br>
connections?<br>
--Definitely an option. I might have something in a back room somewhere,<br=
>
otherwise I have a price for a device that might work. I only wish the<br>
things would present an obvious fault condition; most of the devices<br>
look like they will only fail obviously for a catastrophic event (e.g.<br>
lightning).<br>
<br>
* =A0 =A0 =A0 =A0 Is there a microwave, hair drier, or some other device th=
at<br>
may induce transients on the line? =A0Maybe one of them has a bad power<br>
supply.<br>
-- Quite possible; the room is tight. However the typical room layouts<br>
that student choose put all the appliances near the jack anyway; the<br>
CATV port is there and the refridge/micro tower makes a nice TV stand<br>
(if not terribly sturdy).<br>
<br>
* =A0 =A0 =A0 Various comments about cable running past high voltage equipm=
ent or<br>
facilities<br>
-- There's nothing like that in the hallway ceiling or in the riser<br>
rooms. We traced the cable through the ceiling. Hoped to find damage<br>
where the bundles ended up against pipe hangers, but no dice.<br>
<br>
-Brad<br>
<br>
___________________________________________________<br>
You are subscribed to the ResNet-L mailing list.<br>
<br>
To subscribe, unsubscribe or search the archives,<br>
go to <a href=3D"http://LISTSERV.ND.EDU/archives/resnet-l.html" target=3D"_=
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___________________________________________________<br>
<br>
___________________________________________________<br>
You are subscribed to the ResNet-L mailing list.<br>
<br>
To subscribe, unsubscribe or search the archives,<br>
go to <a href=3D"http://LISTSERV.ND.EDU/archives/resnet-l.html" target=3D"_=
blank">http://LISTSERV.ND.EDU/archives/resnet-l.html</a><br>
___________________________________________________<br>
</div></div></blockquote></div><br><br clear=3D"all"><div><br></div>-- <br>=
Joe Roth<br>Networking Group<br>Binghamton University<br>Ph. 607-777-7528<b=
r>Fax 607-777-4009<br>
</div>
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<p>
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