Finding out whether it's the port or the cable that's broken.

[JKCode]

I've bought a house recently, and it has 5 ethernet ports (wall sockets) in total - 4 of which seem to have full access to the internet via fiber plugged to modem in the attic.

 

My question is - how can one verify whether it's the port (wall socket) or a notably more costly issue - the cable?

[BlueChinchillaEatingDorito]

1 hour ago, JKCode said:

I've bought a house recently, and it has 5 ethernet ports in total - 4 of which seem to have full access to the internet via fiber plugged to modem in the attic.

 

My question is - how can one verify whether it's the port or a notably more costly issue - the cable?

The simplest way without any additional tools is to switch the cable to the port with one that's known good and see if the problem persists. 

 

Say Switch Port 1 -> Kitchen and Switch Port 2 -> Den.

If the network drop in the kitchen isn't working, swap it with one that is known working (Switch Port 1 -> Den, Switch Port 2 -> Kitchen).

 

If the Den still works and the Kitchen does not, then you'll know it's the cabling and a problem with the LAN ports on your switch.

[JKCode]

1 minute ago, BlueChinchillaEatingDorito said:

The simplest way without any additional tools is to switch the cable to the port with one that's known good and see if the problem persists. 

 

Say Port 1 -> Kitchen and Port 2 -> Den.

If the LAN drop I the kitchen isn't working, swap it with one that is known working (Port 1 -> Den, Port 2 -> Kitchen).

I should clarify - by "port" I mean wall socket.

[BlueChinchillaEatingDorito]

Just now, JKCode said:

I should clarify - by "port" I mean wall socket.

For clarity and to follow some industry standard defitions, I'll refer "LAN port" as the ones on your router

and "network drop" as the wall socket.

 

You can still do the same thing. Switch the Ethernet cable that runs from the router to the network drop that isn't working, to a known good LAN port on the router. At the same time, switch the Ethernet cable of the network drop that was working to the LAN port you were having problems. 

[JKCode]

1 minute ago, BlueChinchillaEatingDorito said:

For clarity and to follow some industry standard defitions, I'll refer "LAN port" as the ones on your router

and "network drop" as the wall socket.

 

You can still do the same thing. Switch the Ethernet cable that runs from the router to the network drop that isn't working, to a known good LAN port on the router. At the same time, switch the Ethernet cable of the network drop that was working to the LAN port you were having problems. 

The cable in question is in the wall, it runs all the way to the attic - switching it between ports yields the same result, no internet in the network drop - how can I verify that it's the wall socket and not the cable that runs to the attic that's broken?

[BlueChinchillaEatingDorito]

10 minutes ago, JKCode said:

The cable in question is in the wall, it runs all the way to the attic - switching it between ports yields the same result, no internet in the network drop - how can I verify that it's the wall socket and not the cable that runs to the attic that's broken?

Unless whoever installed the network drop messed up when crimping the twisted strands to the plate, it's pretty rare for a failure in the plate.

 

 

You can get cable testers which will help you verify both continuity and that the stands were crimped in the right order. If even one of the twisted pairs is in the wrong order, it will cause a situation where there's no network connection.

 

https://www.amazon.com/KELUSHI-NSHL468-Universal-Multifunctional-Equipment/dp/B08318BM98/

[Omon_Ra]

3 hours ago, JKCode said:

The cable in question is in the wall, it runs all the way to the attic - switching it between ports yields the same result, no internet in the network drop - how can I verify that it's the wall socket and not the cable that runs to the attic that's broken?

As @BlueChinchillaEatingDorito mentioned, you're going to need to check the terminations. Remove the wall plate, make sure that the wires are punched down the whole way in the keystone jack (the 'wall socket). Also take note of the wiring pattern if it's 'A' or 'B' (90% of wiring is on 'B' pattern from what I've seen). Go to the attic side, and inspect the connector/RJ45 end there. Make sure all the copper/gold contacts are compressed and contacting the wires. Look at the wire colors and make sure they match this image (again, assuming this is a B pattern; also, your wires will not be sticking out the end like this image either). It's kind of hard to tell from this, but from right to left, it's: orange/white - orange - green/white - blue - blue/white - green - white/brown - brown. If you are unsure, take some pics and post them here.

 

 

But assuming the RJ45 end and wallplate are terminated correctly, you'll need to pick up a wire tester/toner. Easily found at any big-box hardware store. There are some cheap ones you can find on Amazon and the like, but if this is the only time you plan on doing this; go buy one, test the run, and return it. You're going to want to do a continuity test and pair identification to make sure there isn't a miswire. It's fairly straight forward and included in the instructions. If it turns out there's a short or cut in the wire, it might not be as awful as you think to repair/replace. But I've seen plenty of runs ruined by any number of reasons and you just don't know until you plug something in and it doesn't work unfortunately.

[Bdavis]

A network tester will tell you if the cable is damaged or incorrectly terminated. It won't tell you if the cable is completely severed. As for budget options you can sacrifice an Ethernet cable by cutting it in half and stripping the insulation on the two cut ends. Next plug the terminated ends in the jacks. You can now connect two wires on one of the stripped end by twisting the stripped conductors in pairs for a total of 4 pairs. Now you can check for continuity on the other end using a multi meter.

 

If you get nothing, the next step is to hook up a tone tester and trace the wire until you find the break.

[Omon_Ra]

6 minutes ago, Bdavis said:

A network tester will tell you if the cable is damaged or incorrectly terminated. It won't tell you if the cable is completely severed. As for budget options you can sacrifice an Ethernet cable by cutting it in half and stripping the insulation on the two cut ends. Next plug the terminated ends in the jacks. You can now connect two wires on one of the stripped end by twisting the stripped conductors in pairs for a total of 4 pairs. Now you can check for continuity on the other end using a multi meter.

 

If you get nothing, the next step is to hook up a tone tester and trace the wire until you find the break.

If none of the pairs match, and they're all '-' or blank..that means cable is cut. But yeah, if that's the case it's a fun journey of tracing back to the cut...or drywall screw through your wire...

[Needfuldoer]

17 hours ago, Omon_Ra said:

If none of the pairs match, and they're all '-' or blank..that means cable is cut. But yeah, if that's the case it's a fun journey of tracing back to the cut...or drywall screw through your wire...

A cable certifier can tell you how far along the run a wire is broken, but those are much more expensive than the blinky-light continuity checkers. 

 

It would also tell you if a cable's termination passes spec, which that keystone above would not. (The wires are untwisted too far, and there shouldn't be dangling bits hanging off the punch. Whoever terminated that one did it backwards.)

 

But unless you want to pay hundreds of dollars for a tool you'll need once, or you can find one you can rent or borrow, you don't need one. It would probably be less costly to replace the run. (99% of the time it's a bad termination though, not a defect somewhere in the middle of a run.)