How to test a bad Ethernet cable

Hello all,

I have a WD TV live HD that has been having issues playing video back. This is how my home network looks:


                                      |                                      (100’)

         Server------- Switch 1  --------------------------------------------  WD Live


                                      |  (35’)


                               Switch 2  ------- PC

                             /             \

                        BluRay       XBOX

Router = WRT54G 10/100

Switch 1 = DLINK DGS-2208 10/100/1000 

Switch 2 = Netgear GS605 V2 10/100/1000

Server = Windows Server 2008 R2 10/100/1000

PC = Windows 7 10/100/1000

WD Live = 10/100

With this setup the video will start out fine and play for 2 to 30 minutes than it will begin to freeze frame. The files are MKVs between 9Mbps and 14Mbps. Now, if I put the WDTV live in my room on switch 2, I have no problems playing the files (streaming from the server). 

If I move my server to the WD Live location and transfer files to the server from my PC, I have no problem hitting 100MBps (800Mbps) transfer speeds. I am wondering if there would be something wrong with the 100 foot Ethernet cable. The cable is made from honeywell CMR 350mhz Cat5e Solid core wiring that I crimped. To make sure it wasn’t a bad crimp I redid both ends. 

I also tried putting a switch between the end of the 100 foot Ethernet cable and the WD live box thinking the WD live box might have a weak Ethernet chip and can’t cope with that long of a distance.

Is there a way to test the cable without buying some fancy fluke equipment? Or is there any other suggestions to resolving my problem.


Yeah, you’re in a pickle.

Short of just replacing them, cable issues are NOTORIOUSLY difficult to troubleshoot without specialized equipment.  The cheap-o consumer-grade switches we buy don’t help, either.

In the enterprise space, our first indications of problems come from errors reported on the port by the switch.   Unfortunately, our switches at home are totally blind.   

You could try swapping the two switches around and see if the problem moves from one place to another.  Also, try swapping ports around.   Short of that, I would recommend you go buy a new cable, pre-made, and see if that fixes your issue.  

CMR, but the way, refers to the building codes (NFPA and NEC) it satisfies, and has nothing to do with its performance.  Cat5e is PLENTY good for everything up to and including Gig Ethernet. `

One other thing you may want to try (assuming it’s practical to do so) if the above sugestions don’t give an improvement: eliminate switch #1.  Plug the server and TV LIve directly to the router, then hang switch #2 directly off of the router as well.  The Ethernet spec allows for cable lengths of up to 100m, so using longer cables may be able to take switch #1 out of the picture.

Most consumer-grade switches often don’t handle being stacked as in your example very well - they’ll usually do it, but can introduce performance issues when run in that kind of configuration, and it usually gets worse as the number of switches involved increases.  Doesn’t always happen, but depending on the quality of the hardware in use that topology may start showing up shortcomings in their design.

I still do have 450 more feet of cable on the spool, I just really didn’t feel like re-running the wire just yet. Looks like that will be my project tomorrow. Also I did try moving the WD Live onto the router and that was still a no go. Have any of you had experience with testing an ethernet cable using a motherboards bios cable tester option? 

Edited Update:

O.K. I just did a reran a temp cable to the WD live box, and it still started skipping. Also the run is more like 60-70 feet than 100. I am unsure what the problem is at this point. The exact same file plays fine in my room off of switch 2 being feed from the server on switch 1. I tried running the WD live off of both switch 1 and the router again. I am wondering if I upgraded to a WD live Hub it that would make a difference.

This is the same cable I can get 800+ Mbps out of putting my server one end and my PC on the other.  I am beating my head against a wall now… lol 

Ok thought I would update one more time. I believe I have found the issue, it is switch #1. No matter what port it is in it still kills the streaming. I tried my second long ethernet cord and connected it to switch #2 keeping everything else the same (including the server on switch 1) and it is working just fine. So it looks like i am going to need a new 8 port switch, sigh…

The moral of the story, don’t buy any network equipment that is labeled as “Green”, even if it’s cheap. 

For the benefit of people searching, please post the exact manufacturer and model number of your switch that you’ve determined is bad.