Short/Crosstalk in Ethernet Line??

The network is the forum.

Moderators: Steel, notfred

Short/Crosstalk in Ethernet Line??

Postposted on Sun Jan 30, 2011 6:57 pm

So I have an 4 port switch (actually a DIR655 router but it acts as a swtich) in my basement and three ethernet cables are connected to it. One feed comes from the router, another feed to a bedroom with a switch in it and the last cable runs to a wall outlet area by my HTPC. The cables are routed through the basement so there is electrical lines all over the place but I strategically placed the ethernet cables perpendicular to any electrical (or cable lines) and as far away as possible. I have a weird phenomenon that has been happening for the last year or so but I mainly live with it. Basically what happens is when I plug in the ethernet cable from that goes to my wall outlet to the HTPC the internet disconnects at the DIR655. When I unplug it the internet returns. Meanwhile network access still works while all the cables are plugged in. The problem is that it is very sporadic when the internet goes down. If I leave the ethernet cable that is giving me problems unplugged for a few days and then plug it back in the internet typically works and my whole network is happy again. Then randomly it will go out again. (by random I mean it happened last night for the first time in four months, but before that it was 3 times in three weeks)

The only thing I can think of is a short in the line or the ethernet cable is not grounded because I have also tried it on a different switch and its the same effect. Anyone ever experience this before or have an idea rather than rerunning the cable (which I probably will have to do)
To Start Press Any Key'. Where's the ANY key?
If something's hard to do, then it's not worth doing
You know, boys, a nuclear reactor is a lot like a woman. You just have to read the manual and press the right buttons.
mmmmmdonuts21
Gerbil Elite
 
Posts: 590
Joined: Wed Jul 16, 2008 9:09 am

Re: Short/Crosstalk in Ethernet Line??

Postposted on Sun Jan 30, 2011 7:10 pm

You typically don't want the Ethernet cable to be grounded, that can cause all kinds of problems with different ground potentials in different places and large ground current flows. Normally things are OK because the Ethernet cable consists of pairs of conductors and differential signalling is used. This means that any interference is in common mode and rejected by the receiver. If you do go to shielded cable then ground it at one end only.

About the only thing I can suggest is to see if any of the motherboard onboard NICs or plugin NICs have a diagnostic program (motherboard one may be part of the BIOS options). These will often not only tell you the speed and duplex of your connection but also the cable run length (they send a pulse and time the reflection from the far end). If those measurements look screwy then I think you are just going to have to re-run the cable.
notfred
Grand Gerbil Poohbah
 
Posts: 3736
Joined: Tue Aug 10, 2004 10:10 am
Location: Ottawa, Canada

Re: Short/Crosstalk in Ethernet Line??

Postposted on Sun Jan 30, 2011 7:25 pm

notfred wrote:About the only thing I can suggest is to see if any of the motherboard onboard NICs or plugin NICs have a diagnostic program (motherboard one may be part of the BIOS options). These will often not only tell you the speed and duplex of your connection but also the cable run length (they send a pulse and time the reflection from the far end). If those measurements look screwy then I think you are just going to have to re-run the cable.


Any program in particular that you have in mind? For some reason this software is very hard to come by.

Also if I do rewire it should I do shielded cables instead of UTP? I don't mind spending a little more to do it right.
To Start Press Any Key'. Where's the ANY key?
If something's hard to do, then it's not worth doing
You know, boys, a nuclear reactor is a lot like a woman. You just have to read the manual and press the right buttons.
mmmmmdonuts21
Gerbil Elite
 
Posts: 590
Joined: Wed Jul 16, 2008 9:09 am

Re: Short/Crosstalk in Ethernet Line??

Postposted on Sun Jan 30, 2011 8:25 pm

have you re-wired the wall outlet and used a different cable from wall to computer?
Matter is merely energy condensed to a slow vibration, we are all one consciousness experiencing itself subjectively, there is no such thing as death, life is only a dream, and we are the imagination of ourselves... back to you with the weather, Bob!
computron9000
Minister of Gerbil Affairs
 
Posts: 2416
Joined: Sun Oct 16, 2005 7:21 pm

Re: Short/Crosstalk in Ethernet Line??

Postposted on Sun Jan 30, 2011 8:42 pm

I feel for you. First, I would make damn sure the wires in the walls are actually bad. So, for the wire that you think is bad, run another wire from the router to that computer or whatever. Test that out. If it does the job, then yea, maybe the wire in the wall is bad and a reroute might be needed.

From all my years of construction, I have always heard that having shielded wires (any and all kinds of wire) in a wall were always a way to go. It is a precaution to many things and reasons. And if you have to reroute then just tape the new wire on one end of the wire in the wall and pull it thru. It is really easy to do. Just tape it good cuz really, you only have one chance at it. ;-)

Hope that helps.
A fact is a simple statement that everyone believes. It is innocent, unless found guilty. A hypothesis is a novel suggestion that no one wants to believe. It is guilty, until found effective.
Edward Teller
SomeOtherGeek
Gerbil First Class
Gold subscriber
 
 
Posts: 166
Joined: Fri Jun 06, 2008 7:49 pm
Location: Outside somewhere

Re: Short/Crosstalk in Ethernet Line??

Postposted on Mon Jan 31, 2011 9:18 am

mmmmmdonuts21 wrote:Any program in particular that you have in mind? For some reason this software is very hard to come by.
I agree on hard to find. My desktop at home has a it built in to the motherboard BIOS (EP43-DS3R). There used to be more of them around back in the ISA NIC days, the beloved 3C509 had a great little utility suite that booted from a floppy. It's going to be something specific to the NIC model as it is going to read non-standard registers in the Ethernet PHY device, so you are relying on the NIC manufacturer for this unfortunately.

mmmmmdonuts21 wrote:Also if I do rewire it should I do shielded cables instead of UTP? I don't mind spending a little more to do it right.

SomeOtherGeek wrote:I have always heard that having shielded wires (any and all kinds of wire) in a wall were always a way to go. It is a precaution to many things and reasons.
See my earlier post. You have to be very careful with the grounding of the shield otherwise you can get quite large currents and blow things up in the worst case, or have it act like an aerial and add more interference. It's generally not recommended.

One other thought, I wonder if you are simply running in to too long a cable. How long is the cable(should be less than 100m/328ft)? What is it rated at (Cat 3, Cat5, Cat5e)? What speed does your HTPC negotiate at (10Mb, 100Mb or 1000Mb)? Note that 1000Mb requires all 4 pairs to be working in Cat 5 or better whilst lower speeds use only one pair in each direction.
notfred
Grand Gerbil Poohbah
 
Posts: 3736
Joined: Tue Aug 10, 2004 10:10 am
Location: Ottawa, Canada

Re: Short/Crosstalk in Ethernet Line??

Postposted on Mon Jan 31, 2011 10:36 am

notfred wrote:One other thought, I wonder if you are simply running in to too long a cable. How long is the cable(should be less than 100m/328ft)? What is it rated at (Cat 3, Cat5, Cat5e)? What speed does your HTPC negotiate at (10Mb, 100Mb or 1000Mb)? Note that 1000Mb requires all 4 pairs to be working in Cat 5 or better whilst lower speeds use only one pair in each direction.


Its a Cat5e cable and the run is about 40-45 feet. The HTPC has a P35 MB in it with a realtek NIC at 1000MB. So I think what I am going to do is just replace the cable with a standard STP Cat6 cable after I verify once again its not the HTPC causing the problems.
To Start Press Any Key'. Where's the ANY key?
If something's hard to do, then it's not worth doing
You know, boys, a nuclear reactor is a lot like a woman. You just have to read the manual and press the right buttons.
mmmmmdonuts21
Gerbil Elite
 
Posts: 590
Joined: Wed Jul 16, 2008 9:09 am

Re: Short/Crosstalk in Ethernet Line??

Postposted on Mon Jan 31, 2011 11:05 am

Can you try forcing it to 100MB? When I moved in to my house the run to the HTPC had a staple through it and it would work at 100Mb and not at GigE as the damage was to one of the extra pairs. If that works for you then I'd agree that replacement with Cat6 should get you going again.
notfred
Grand Gerbil Poohbah
 
Posts: 3736
Joined: Tue Aug 10, 2004 10:10 am
Location: Ottawa, Canada

Re: Short/Crosstalk in Ethernet Line??

Postposted on Mon Jan 31, 2011 11:12 am

Okay. I will try that when I get home tonight first. Thats probably what happened with a staple or something.
To Start Press Any Key'. Where's the ANY key?
If something's hard to do, then it's not worth doing
You know, boys, a nuclear reactor is a lot like a woman. You just have to read the manual and press the right buttons.
mmmmmdonuts21
Gerbil Elite
 
Posts: 590
Joined: Wed Jul 16, 2008 9:09 am

Re: Short/Crosstalk in Ethernet Line??

Postposted on Mon Jan 31, 2011 8:42 pm

So I tried hooking up the cable to an Xbox (which is only 10/100mb) connection and it worked with out issue. When I tried plugging it back into the PC the connection drops like it did before. So bottom line I think something is wrong with one of the pairs, so it looks like I will be replacing the cable in the next few days or so once I get my shinning new CAT6 (should I go CAT6A from monoprice instead?) cable in. Thanks for the help again.
To Start Press Any Key'. Where's the ANY key?
If something's hard to do, then it's not worth doing
You know, boys, a nuclear reactor is a lot like a woman. You just have to read the manual and press the right buttons.
mmmmmdonuts21
Gerbil Elite
 
Posts: 590
Joined: Wed Jul 16, 2008 9:09 am

Re: Short/Crosstalk in Ethernet Line??

Postposted on Tue Feb 01, 2011 8:38 am

If there is not much difference in price then I would go to the Cat6A, it's meant to be able to support 10GBASE-T as the pairs are good to 500MHz rather than 250MHz for Cat6
http://en.wikipedia.org/wiki/Twisted_pa ... categories
notfred
Grand Gerbil Poohbah
 
Posts: 3736
Joined: Tue Aug 10, 2004 10:10 am
Location: Ottawa, Canada

Re: Short/Crosstalk in Ethernet Line??

Postposted on Tue Feb 01, 2011 9:04 am

I just decided to run a Cat6 cable I have around my house rather than buying a new Cat6a because they were out of stock in the 50ft length at monoprice.
To Start Press Any Key'. Where's the ANY key?
If something's hard to do, then it's not worth doing
You know, boys, a nuclear reactor is a lot like a woman. You just have to read the manual and press the right buttons.
mmmmmdonuts21
Gerbil Elite
 
Posts: 590
Joined: Wed Jul 16, 2008 9:09 am

Re: Short/Crosstalk in Ethernet Line??

Postposted on Tue Feb 01, 2011 9:14 am

mmmmmdonuts21 wrote:So I tried hooking up the cable to an Xbox (which is only 10/100mb) connection and it worked with out issue. When I tried plugging it back into the PC the connection drops like it did before. So bottom line I think something is wrong with one of the pairs, so it looks like I will be replacing the cable in the next few days or so once I get my shinning new CAT6 (should I go CAT6A from monoprice instead?) cable in. Thanks for the help again.

This could also be an indication that there's something wrong with the HTPC -- like the NIC behaving wonky, or a software issue (misconfiguration or malware) that is generating excessive network traffic or triggering broadcast storms.
(this space intentionally left blank)
just brew it!
Administrator
Gold subscriber
 
 
Posts: 37705
Joined: Tue Aug 20, 2002 10:51 pm
Location: Somewhere, having a beer

Re: Short/Crosstalk in Ethernet Line??

Postposted on Tue Feb 01, 2011 10:04 am

just brew it! wrote:This could also be an indication that there's something wrong with the HTPC -- like the NIC behaving wonky, or a software issue (misconfiguration or malware) that is generating excessive network traffic or triggering broadcast storms.


Is there anyway to test this NIC behavior? It occurs so randomly and infrequently that it is nearly impossible to see if it happens on a different computer or not. Its a Marvell Yukon NIC. I don't think its a software issue because I have reinstalled a fresh copy of windows 7 on the computer 3 times in the past year or so (the last time about two weeks ago when I put an SSD in the HTPC).

I mean I was having issues when the HTPC was turned off but still plugged in. Last night, after I turned the computer on with the ethernet cable not attached, and once the computer booted up I got it to work very late last night on the HTPC as well (on the old cable). First I only tried the 100mb connection and then I boosted it back up to 1gb. It worked flawlessly. I also tried a network tester with the connection and their was no indication of a problem at all in any of the lines.
To Start Press Any Key'. Where's the ANY key?
If something's hard to do, then it's not worth doing
You know, boys, a nuclear reactor is a lot like a woman. You just have to read the manual and press the right buttons.
mmmmmdonuts21
Gerbil Elite
 
Posts: 590
Joined: Wed Jul 16, 2008 9:09 am

Re: Short/Crosstalk in Ethernet Line??

Postposted on Tue Feb 01, 2011 10:13 am

Gonna be very hard to test since it happens so infrequently. Have you tried installing the latest Marvell reference drivers?
(this space intentionally left blank)
just brew it!
Administrator
Gold subscriber
 
 
Posts: 37705
Joined: Tue Aug 20, 2002 10:51 pm
Location: Somewhere, having a beer


Return to Networking

Who is online

Users browsing this forum: Google [Bot] and 3 guests