Question about Ethernet Cable

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raindy88

Nov 10, 2018
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Hi,

Recently I just upgraded my internet speed to 300mbps, however, my speed only can reach around 98mbps instead of 300mbps.

My current network layup is

Desktop > RJ45 faceplate wall socket end with RJ45 Male > Switch > Router

all my cable are using Cat5e, trying to troubleshoot the problem by myself I found no problem with the cable, if I connect my desktop to switch, it can reach 300mbps. But if connect through a wall socket, it only reaches around 98mbps.

So I checked the keystone, it's Cat5e, with both end using T568A.

May I know why if I connect through wall socket it will be capped at 98mpbs? and what's the solution for this?

I check all my devices, all of it are able to support Gigabit Ethernet, and all cable are using Cat5e UTP straight through cable with t568a standard

Sorry for the terrible English
 
Solution
B
You want both ends the same. Cross over cables do mess up the speed negotiate some times. It is very random but it is common for ports to drop to 100mbps if you use crossover

You pretty much don't need crossover cables any more. Almost all ports including those that only run 10/100mbps have what is called auto MDIX. It will negotiate and in effect make crossover connection.

Gigabit does not really have the concept of crossover. It transmits and receives on all 4 pair on both ends of the cable at the same time. Almost magic it can do this when you consider how stupid 10/100 is.
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bill001g

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Aug 9, 2012
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Unfortunately a cable tester that can really verify that all the wire pairs can pass data properly cost more than most home users can afford. There are cheap simple cable testers than can verify connectivity on the wires but they can not for example detect that the pairs of wires are hooked to the wrong pins.

It almost has to be one of the wires....likely the brown or blue pair...not making proper contact with internal pins in the wall jack. No way to tell just by looking at it. Most times it is trial and error cutting off a very small amount of the end of the wire and re punch it into the jack. There is no way to know which end or which wire is causing the problem without expensive tools.

It could be a defective jack but that is not real common. The wire itself luckily tends to not be the problem unless it gets damaged say by a nail or maybe a mouse chewing on it.

.....noticed after rereading that you might not be using wall jacks with rj45 keystones. If you have the crimp on plugs those can be tricky to crimp on for people that don't do it a lot. A keystone is a little more expensive but tends to be simpler and you can try multiple times if you mess up.
 
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raindy88

Nov 10, 2018
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0
10


it's actually a small office which 5 other PC also using the same setup. (Desktop > Wall plug with end of the side connected to Switch> Router) and all of it having the same issue. When connecting via wall plug, it's limited at around 98mpbs. If direct Desktop > Switch > Router then I can reach the speed of 300mbps
 
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bill001g

Titan
Aug 9, 2012
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Almost sounds like someone mis wired all the jacks. What you are describing pretty much means the ports are running at 100mbps.

You have eliminated the electronics as the source of the problem by directly connecting with a ethernet cable. This only leaves you in wall cabling.

Maybe buy one of the cheap testers like this since you have so many jacks to test.
https://www.amazon.com/Flexzion-Network-Ethernet-Indication-Countunuity/dp/B017SM0G1U

It does not do much but it is very cheap, there are many other brands this is just a example.

You might get lucky and find it with this.

You need to carefully recheck to be 100% sure the wire colors follow the 568a you say you have.

This is actually pretty simple but it is surprising how hard it is to get right many times. The port speed negotiation when it drops to 100mbps almost always means it is not getting signal on all 4 pairs. If it was not getting signal on the orange and/or green pair most times the port will not come up at all.
 
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raindy88

Nov 10, 2018
3
0
10


Thank for your patience answering my question

I'll try to get a tester.

I read something about crossover and straight through cable. For wall jack which type of cable should be used? If wall jack's keystone using T568A, another end (RJ45 Male) that connect to switch should be same or using T568B? is that possible they mess up that part and causing the problem?

 
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bill001g

Titan
Aug 9, 2012
28,283
2,743
125,640
You want both ends the same. Cross over cables do mess up the speed negotiate some times. It is very random but it is common for ports to drop to 100mbps if you use crossover

You pretty much don't need crossover cables any more. Almost all ports including those that only run 10/100mbps have what is called auto MDIX. It will negotiate and in effect make crossover connection.

Gigabit does not really have the concept of crossover. It transmits and receives on all 4 pair on both ends of the cable at the same time. Almost magic it can do this when you consider how stupid 10/100 is.
 
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