[SOLVED] Can a broken Cat5E cable produce slower speeds?

Feb 28, 2019
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Hi All,

I am upgrading my network and added a better router. In the process I had to fix a cable that's running outside my house with new RJ45 ends which seemed to do the trick. I noticed occasional drop outs in the connection. Streaming videos from my NAS would lock up for 30 seconds, that sort of thing. So I am going to replace it at the weekend. I seem to be now be getting reduced speeds from it, not full gigabit as it was yesterday.

==TLDR
My question is this, can Cat 5E cable simply be bad, I assumed it would either work, or not work, or perhaps work intermittently. I've never seen reduced speeds in this way before. Is this possible?

I am asking as I want to know will replacing just this one cable help my problem or do I need to dig deeper?

==TLDR END

More detail:
This morning I am getting internet speeds of < 100Mbs when I normally get 3-4 times more than that.

So I used iperf to test LAN connections from my main PC to my laptop from the 2 switches and finally the router that leads my PC to the internet. PC > Switch 1 > Switch 2 > Router > Modem.

From both switches I get full gigabit, but from the router I only managed 105Mbs. I tested this the same way on the day I put it all together and definitely got full gigabit everywhere.
 
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You are correct it should just work. Cables are normally not that stubborn. I always test if at all possible with the cable in the same room as the router all coiled on the floor before I run it.
I also use keystone jacks on cable that is pulled through walls just because it is easier to hookup that crimping on rj45.

A note on cable. Make sure you are buying pure copper cable. That crap CCA cable is not a certified cable and has issues with distance. The end tend to come loose over time because of the dissimilar metals. Also make sure all your cable have wire size 22-24 awg. Those flat or thin wires are also not certified cable and have issues.
 
Cables can run slower for a couple reasons. The most obvious is the signal is poor enough that the devices on the ends drop the speed to 100mbps or maybe even 10mbps. The other less common one is that you are getting data errors. Unlike wireless the packets are just discarded but the applications then retransmit the data which decreases the total data sent. Commercial equipment has packet error counters so you can see how many packets the interfaces discard for some reason consumer equipment does not have that. It makes it hard to know if you are getting errors on a ethernet cable.

The cable itself is seldom the issue but it can be if say it got a nail in it or it gets wet or maybe some animal chewed on it.

It is the ends that tend to cause the most issues. You can one pin that barely makes contact and it may work and then as it gets warm the metal expands and it disconnects
 
Feb 28, 2019
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Thanks for your input and at this point I am very confused.
  1. I have replaced the cable with a new one, I had an extra long length and ran it through the wall and again got limited speed, both ends I made today.
  2. I then cut the cable in half (as it was really long) and replaced the end, still slow.
  3. After that I took the remaining length I cut off and made a new cable and ran that, again slow.
It is a category 5e cable, and the RJ45 connectors I have been using look fine. Since I've used a bunch now I am perplexed as I have now technically tried 3 cables (even if was was split and used again).

I know it is this specific cable/connection as I have tested between 2 machines at every point in the network and get gigatbit speeds everywhere except when this connection/cable is involved.

Only thing I can think of is to buy a brand new cable and try a forth (or is it fifth) time.

Am I correct in thinking it only needs to be these 4 things to work:
  • Category 5E or greater cabling
  • Less than 100 Meters in length
  • Straight Through Wiring Type (like this)
  • Standard RJ45 Connector
Is there anything I am missing? I feel like I'm taking crazy pills.

Thanks again,
 
You are correct it should just work. Cables are normally not that stubborn. I always test if at all possible with the cable in the same room as the router all coiled on the floor before I run it.
I also use keystone jacks on cable that is pulled through walls just because it is easier to hookup that crimping on rj45.

A note on cable. Make sure you are buying pure copper cable. That crap CCA cable is not a certified cable and has issues with distance. The end tend to come loose over time because of the dissimilar metals. Also make sure all your cable have wire size 22-24 awg. Those flat or thin wires are also not certified cable and have issues.
 
Feb 28, 2019
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Thanks, it does look kinda shonky, plus it's not copper and pretty thin (but not the flat kind). Guess I should buy something decent and not use whatever I find in the cupboard.

I tried the second length I made in the same room and get slow speeds too. Next stop is the bin (or recycling).

Thanks for you help, just wanted to be sure I was doing everything right, been a few years since I've needed to do anything.
 

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