Long Ethernet cable and router problems

[Sin97525]

I recently built a PC and would like to use Ethernet connection on the second floor, so I ran a 15 meters Ethernet cable to connect to the router at the basement, but I'm not getting any connection.

 

My setup was this: modem -> router -> 15m cable(cat 5e) -> second floor -> PC

With this setup, I don't get any connection through the cable. I have checked with another desktop computer and 2 other laptops and they all resulted in the same thing; windows either say network cable unplugged or unidentified network if it recognizes the cable.

 

I then changed the setup to this: modem -> 15m cable -> second floor -> router -> PC

And now everything is working, I get full speed and everything is perfectly fine, but I can't put the router on second floor since I have other things(server, other computers) connected to the router via Ethernet at the basement.

 

I also tried directly connect the PC to the modem with the 15m cable and that also worked. Now it seems to me that the problem comes from the router, but I'm not sure what the problem is.

I was thinking it may have to do with resistance, but that shouldn't be a problem since 15m isn't that long. Any thoughts guys? I really need help on this.

 

P.S. router model is Linksys ac1600

[Electronics Wizardy]

Assuming everything else is good, its probably a bad cable. RJ45 can have some issues with that length, so either limit it to 10 or 100mb/s or get a cat 6a or fiber cable.

[Kishi]

You're usually okay as long as it's shorter than like 100ft with 5e, in my experience.

[Donut417]

Networking cable is generally good to 100m or just over 300 feet. I would say it might be a bad cable. 

[2FA]

The actual power of the signal that the router puts out across the cable might be too weak to travel that distance. 

[Jack Dvorak]

do you have any dsl outlets upstairs? if so, put the modem and router up stairs.

[ThomasD]

Weird.

 

I agree that it sounds like the output of the router doesn't like a 15 meter run.  Is their only one out on the router? If not have you tried each out?

 

Your cheapest and easiest option is to make another 15 meter run and give it a try.  Alternately you could get an inexpensive 5 port switch and connect it with a short run off the router, then the long run off the switch. 

[RedShift1]

If the router cannot handle a 15 m cable, it's violating the Ethernet standards. Ethernet allows for 5 m of stranded wire, 90 m of solid core wire followed by another 5 m of stranded wire. So let's first check what type of cable you have running now, is it stranded or solid? Also make sure the cable is of a decent brand, there is known bad cabling out there, where something other than copper was used. Other cable issues might be improper twisting, which can derived from measuring the length of the individual pairs, they shouldn't be too dissimilar in length.

Next, you should check if the endpoints are wired correctly. You should be using T568B wiring (see https://en.wikipedia.org/wiki/TIA/EIA-568#T568A_and_T568B_termination for pinout). You should also verify the endpoints using an Ethernet testing device, most of them are simple lights that don't tell you much, there are more advanced measuring devices such as those sold by Fluke which can tell you a lot more and detect faults the simple testers can't.

If that all comes back good, one of your devices is not within spec and you should return the device to the seller.

Edit: Just to alleviate any confusion, cat 5e is suitable for 1 gigabit speeds up to 100 m. You don't need cat 6 for that. Also check if your cable isn't running next to power cables, especially when it's unshielded. And even with shielded cables, I've seen cases where Ethernet cables stopped working when ran right next to power cables.

[Curlz]

I'll just add to the above post. If you do find out its interference causing the problem, CAT6 cable is more resistant to interfeeence than CAT5e.

[Sin97525]

Thank you everyone for replying.

 

I have been doing some diagnostic for the past 2 days and have switched to a 15m cat6 cable.

Now a new problem comes, I'm not getting 1Gbps connection, but only 100Mbps. I even tried it with other computers. The router is compatible with gigabit connection and other devices that are connected to it(using other cables, all cat5e) are getting 1Gbps. 

 

I'm really starting to think that the router is the problem, but I still can't see why is that. With cat5e I'm not getting connection at all and with cat6 cable I only get 100Mbps. In fact the 15m cat5e cable is industrial grade ethernet cable that I got from my workplace, and it is working if I directly connect the modem to my PC, so quality shouldn't be a problem. Any new thoughts on this?

 

[dalekphalm]

On 2016-09-23 at 10:03 PM, Electronics Wizardy said:

Assuming everything else is good, its probably a bad cable. RJ45 can have some issues with that length, so either limit it to 10 or 100mb/s or get a cat 6a or fiber cable.

Err what are you talking about? Cat 5e is rated up to 100m (330ft) and can run Gigabit Ethernet at those speeds.

 

15m should literally be a piece of cake for a properly terminated cable.

 

With that in mind, he could easily have a bad cable, as you say, but that wouldn't be because it's Cat 5e, but simply because it's a bad cable. If the cable was Cat 6 or Ca6a, and was still bad, he would have the exact same issues.

 

@Sin97525, did you buy this cable or make it yourself? Either way, I'd recommend picking up a cheap cable tester:

https://www.amazon.com/Tonor-RJ45-Network-Cable-Tester/dp/B00OUFX38W/ref=sr_1_1?ie=UTF8&qid=1474907962&sr=8-1&keywords=rj45+cable+tester

$10 - Monoprice sells the same one (branded Monoprice of course), for those who prefer to shop there, I think it's a couple bucks cheaper too.

 

This is a great tool for any techie person to own. It's just a simple tester though - it won't show you distance faults (some of the more expensive models and pinpoint a break in the cable, and tell you how far along the cable it is, eg: 5.8m down the cable).

 

Could be a bad cable, as mentioned. Did you plug everything into the right ports? Eg: Modem -> WAN Port of Router -> 15m cable goes from regular LAN port to PC.

[mmorrone]

I recently just bought a powerline solution for pretty much the same thing, being that I am directly under the router but the only stairs to my floor is on the other side of the house. While yes, it is not the wired connection that everyone wants, but I am still getting 1Gbps LAN speed. Linus did a video for this one (for NCIX) and got severely degraded signal as compared to a direct ethernet connection, but I am thinking that is mostly the wiring setup of the building, as well as the size of the building he tested it in. Without an electrical routing schematic, it is hard to tell.

Video shown here: