I have a long ethernet LAN cable buried in the wall and replacing the the whole thing is not an option.

I simply want to extend the cable a bit without bringing a network guy home. I have lots of ethernet cables.

I think the LAN is Gigabit Ethernet (I'm not sure, but I can check if it's needed).

My question is - what I need to do is buy a RJ45 and simply connect another ethernet cable at the other end, and connect it to the computer? Or something else?

  • Google 'ethernet extender cable'
    – Tetsujin
    Aug 5, 2015 at 11:47
  • I did, that's how I came up with the RJ45, but I want to make sure it does what I think and that it will work with Gigabit ethernet.
    – traveh
    Aug 5, 2015 at 11:48
  • I also checked on Wikipedia but it wasn't completely clear to me.
    – traveh
    Aug 5, 2015 at 11:49
  • you just need a female to male instead of the usual male to male. Anything cat 5e or up ought to do it, unless you're really going a long way, in which case cat 6
    – Tetsujin
    Aug 5, 2015 at 11:50
  • Hmm I googled female to male and it I think what I need is female to female little box thingy, if I already have the extra male-to-male cables, no?
    – traveh
    Aug 5, 2015 at 11:54

2 Answers 2


Presuming that you won't be breaking the 100-Meter maximum lenght specification, a simple gender-swapping coupler should allow you to connect the two cables as you describe. There are a couple potential gotcha's however.

First, both cables would should use a compatible wiring scheme. Standard ethernet cable uses a Straight-Through layout, but there are also several other layouts, such as Cross-patch/Cross-over. If the cable in the wall is cross-over, be sure to use a straight-through cable to extend. Most combinations will work, but there are a few to be careful of, especially if the nics in one of the connecting devices don't support auto-pin mapping (MDI-X)

Second, you may notice that after installing the coupler, that power/signal drops, and you are resending more signals than is optimal. in that case, some kind of active repeater/bridge/switch will be required. if you have seen powered devices online, these are essentially single port repeaters, which boost signal as it passes through. Note however that a repeater is an analog technology, and will amplify noise as well as it amplifies desirable signal. if there is too much noise on the line, only a fully fledged digital device like a switch or bridge will fix that.


The simplest method is to use a coupler known as a RJ45 Coupler. It is simply two RJ45 sockets connected straight through and allows you to plug in the ends of two Ethernet cables to effectively extend the length. They can be found for pennies on popular on-line auction and electronic/computer retail sites.

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  • 9
    nice use of mirror. Aug 6, 2015 at 11:43

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