Stange cat 6a cable problem

[Thomas_baas]

I recently bought myself 100meter (328 feet) of cat 6a cable, rated for 10Gigabit speeds. I will only use it for 1 Gigabit speeds. The problem is that the cable only works on 100mbps, if you force you network card to 1Gigabit the light from my network port will flash for 1 second and then stop to begin this proces again 1 second later.

 

If i test the cable it shows me that all of the 4 pairs work fine, only the ground doesn't work. Can this be the problem? I also called the shop were I bought the cable and they said that it was a problem with the lenght of the cable, but I won't believe this because the cable isn't longer then 25 meters (82 feet).

 

I also checked that the network card of the computer that I used was Gigabit, which it was. Also everthing in my network is 1 Gigabit.

 

Maybe you guys know a solution.

[brwainer]

Did the connectors on each end come preindtalled or did you put them on yourself? If the latter, I'd recommend carefully reterminating them, and make sure you have the same wire pattern at each end. You can have a situation where the tester says everything is fine, but actually one end has a loose wire, or the two ends have mismatched pins such that 100Mb works but not gigabit. Make sure there is no damage in the wire anywhere - knicks, etc. Possibly get a better line tester that will tell you the length of each pair and test from both ends to make sure that the measurements all come out the same - if they don't, you have a damaged wire.

Are you plugging both ends directly into devices, or is one end going into a walljack or patch panel? If there is a walljack or patch panel, I'd suggest reterminating it for the reasons above, and doing the same length test.

Have you tested that both devices are able to link at gigabit using a different wire, or with other devices? Have you tested whether other devices can link at gigabit using the wire in question?

I work for an ISP that only provides service in apartment complexes via ethernet ports in the bedrooms and living rooms of the apartments (very similar to the way an office building is wired). For premade wires, most problems come from wire damage and/or the wire being tripped over or similar trauma that breaks the wire at the connector. For wires that are hand terminated, most problems are from the termination, and sometimes from the walljack being destroyed by someone moving furniture. Sometimes the wire gets damaged inside the wall, by rats or maintenance or old age (over 10 years old usually). Occasionally but rarely the switch port or client device has a jack that has been damaged or just mysteriously goes bad in weird ways. I have seen a desktop NIC that linked at gigabit before a thunderstorm, but only 100Mb half duplex after the storm.

If the wire is not damaged in any way, and the devices are working, then I would question if they really sold you Cat6a cable. You can't call something Cat6a unless it tests positively for 250MHz over 100 meters.

[leadeater]

@Thomas_baas Sounds like the cable is faulty. For 1Gbps and higher connections all 4 pairs are used for data transfer, if only 1 wire is damaged it will either revert to 100Mbps or not work at all depending on which wire is damaged. Get the cable tested to make sure is it in good working condition a simple continuity test does not always show faults.

 

Edit: Also that shop that said it was a length issue has no idea what they are talking about. Cat 6a is rated for 10Gbps over 100m, anything labeled as Cat 6a must meet the required rating to be called as such. Print out the standard from Dynamix or even wikipedia and show it to them.

[beau]

what Standard did you use to terminate the ends?  T568A or T568B?

You can't just make up whatever pinout you want because each twisted pair has a different twist ratio, and if you're using a pinout different to the two standards may mean your signal is interfering with itself even if it passes the continuity test.

[Thomas_baas]

I have used a patch panel and a walljack, everthing in my house is T568B. I know for sure that I didn't mix the A and B standard up. I do have some of that wire left so I can cut of some of that and put on 2 rj-45 plugs.

[brwainer]

I have used a patch panel and a walljack, everthing in my house is T568B. I know for sure that I didn't mix the A and B standard up. I do have some of that wire left so I can cut of some of that and put on 2 rj-45 plugs.

That's good so far, but I would still check your terminations to be sure you didn't mix up two wires or one or the wires didn't make a good connection. Please test with a line tester that is capable of doing full tests such as wire length, short, wiremap, etc. The cheapest unit that I've used with all the features you should test your wire for is a model NF-8208, from a no name Chinese brand that's available on Amazon. My employer has bought a bunch of them and they have been a great help over models that just give you 8 LEDs that light up.

As an example, I was testing a bunch of runs yesterday and the tester found results such as pins 7 and 8 swapped at one end (Brown and White-Brown), a short on pins 4 and 5 (Blue and White-Blue), and a line that measured 60m on three pairs but only 15m on the last pair - turned out to be a nail that went through the drywall and pierced the line. All three of these issues might not be revealed by a tester that only gives you an LED that lights up for each wire.

If you already have a tester that is capable of displaying your wiremap and the pair lengths, please let us know the results.

[Thomas_baas]

I know that my d-link switch is capable of detecting a mismatch, a short and open in cable. When I force my computer to 1GBps speed it shows mismatch in cable in ALL of the pairs, even though pair 2 en 3 where working correctly at 100MBps. I got 2 testers now, 1 that shows me each wire individually and 1 that shows me the pairs.

[brwainer]

I've seen the feature in Dlink Smart switches you are referring to, and I do not find that it is reliable - it has given me too many false negatives.

[brwainer]

Once you've proven to yourself that the wire should be working properly, i.e. you know for certain it is well terminated with no mismatches and there is no damage to the wire, and you know that your devices can link at gigabit using another wire, you should go back to the store with the specifications of Cat 6a and ask them what's going on - since at that point it should be good to carry the signal for 100meters. From my experience and what you've told us, either they didn't sell you Cat 6a, the wire has gotten damaged, you have a termination problem, or your hardware is damaged.

By the way, have you checked the patch cables you are using at either end, to make sure they're not the culprit?

[Thomas_baas]

Does it help if I buy metal rj-45 jack instead of plastic ones?

[braneopbru]

Does it help if I buy metal rj-45 jack instead of plastic ones?

No, it won't make a difference for 1Gb.

 

You said that you are using wall jacks with patch cables. Take the patch cables and connect them between devices to make sure that they both allow a connection at 1Gb. Are the patch panels and wall jacks that you used high quality and were the connection punched down properly?

 

I'd say that is a poor punchdown connection. There's just enough contact for your meter to read a connection but it's to high resistance for the NIC to use as a signal line.

 

Even if they sold you a shit cable that's only cat5 and only does 100Mb - which I don't believe; where would you even find that - if there is a good connection, your card should at least be able to negotiate 1 Gb link, then just start throwing out packet errors once you try to send anything.

 

if you have a standard multimeter, run a quick test. Take a small, junk patch cable and cut it in half. On one half, connect each of the colour pairs together and plug it in to the wall jack. On the other half, connect it to the patch panel and use your multimeter to test resistance across each colour pair. The resistance across each of the four pairs should be identical. If it's not, you know that either your punchdowns are bad or the cable is damaged. Once you figure that out, you can troubleshoot further.

[IceWulf]

Your pinout is likely to be wrong if the 4 pairs are fine.

 

 

 

Notice how it's ALWAYS white/color before color (i.e. White/Orange then Orange) EXEPT for the 2 in the middle which are Blue first and white/blue second. Please check your pinout and fix it accordingly.

[Thomas_baas]

I'am going to test this all, starting by connecting 2 computers on to it.

[Scheer]

Its very likely faulty punchdowns, try re-terminating each side a few times (just repunch each wire a few times to make sure its fully seated). I've ran into this issue a few times now with my Cat6a since I am using standard Cat5e patch panels and keystones, it will pass a cable test but I only get 100mbps.

 

A proper impact punch tool used with a keystone support block will really help. The little plastic tool that come with a lot of the keystones is a complete POS.