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View Full Version : Need help troubleshooting cable failure; also, which standard (T568A or T568B)


Abe18
06-10-2009, 02:58 AM
Can you help me to troubleshoot why a recently installed CAT-6 cable doesn't work?

A general building contractor was hired to fish wire through the walls from our basement router (D-Link DIR-655) to an upstairs office 70 ft. away. Previously, the upstairs laptop connected to home network using D-Link DWA-642 wireless adapter. The contractor used bulk wire and attached the RJ45 connectors. However, once attached to the router and laptop, with wi-fi disabled, the laptop could not access the router. To make sure that the laptop itself was properly configured, I brought laptop into close proxmity with the router and used a store-bought cable to connect the laptop to the router. Once connected with the store-bought cable the laptop could access the internet AND the home network.

Since connection with contractor-installed cable has not occured, the contractor sent me the following website and asked me to tell him which configuration to use:

http://www.ertyu.org/steven_nikkel/ethernetcables.html.

Because the distance is fairly long, I am guessing that I will want to have a CAT-6 solid wire cable. That suggests the contractor needs a special solid-wire crimp tool to successfully connect the solid-wire cable to the RJ45 connectors. Is there anything else I am overlooking?

Finally, which RJ45 jack style should I use: t568A OR t568B? Does it make any difference which protocol is used for the wiring?

Abe18

YeOldeStonecat
06-10-2009, 07:40 AM
568b is the more commonly used standard, from what I've read around various forums....568a is used more commonly in the UK..and that's about it. I've never seen 568a used here in the States.

Ultimately it doesn't matter which is used...as long as the same standard is used on both ends of the cable. You can mix cables of A and B in the same router and/or switch....as long as each cable has its ends terminated in the same standard.

When bulk cable is used...to make runs in an office or house or whatever...those spools you purchase are usually solid, not stranded. Technically the ends that you crimp on are specifically made for one or the other..the way they "pierce" when you crimp them is different. There are some ends (siemens makes one) that will work for both. But the majority of ends that you purchase are designed for solid...since when you terminate your own cables you're doing runs from spools which are solid.

Stranded cables are used more commonly in factory made patch cords, they're more flexible...and more difficult to get a good crimp on..but you're usually never terminating those yourself.

Since you tested your computer and the router using your own shorter patch cable and it worked....my hunch is that the contractor that did the CAT run for you wasn't all too familiar with properly crimping ethernet.

I'm rarely comfortable when I have to setup a network and I heard that some contractor already ran and terminated the ethernet cables....as experience over many years of doing what I do has shown me that contractors frequently do a poor job of it....and I'll be wasting many hours of troubleshooting and having it re-done.

thiggins
06-10-2009, 09:38 AM
YeOldeStoneCat's advice is spot on. Doesn't matter which standard as long as both ends are terminated the same. See How To: Diary of a New Home Network- Part 2 (http://www.smallnetbuilder.com/content/view/24217/229/).

Abe18
06-10-2009, 11:03 AM
Thanks, for your help. I have passed this on to our contractor.

Abe18

thiggins
06-10-2009, 11:20 AM
And make sure that he tests the terminated runs. A bandwidth / performance test isn't necessary. But he at least needs to test with a LAN cabling continuity checker like I used (http://www.smallnetbuilder.com/content/view/24835/229/1/3/).