Ethernet Cable 100m extension. Is that 100m in total?

[Brett-L]

I realise I should know the answer to this but I need confirmation from an expert!

I have fibre and a BT Smart Hub 2. I'm getting about 140 Mb/s. I'm looking to extend the broadband to an outbuilding that's about 80m from the router. I know that the limit for an ethernet cable is 100m.

Is that: 100m measured from router to PC, or is it just 100m for any one unbroken length of cable?

ie Could I go: router to ethernet switch with 10m of cable, then 100m of unbroken ethernet cable underground (Cat 6 or 7), then another switch at the far end and a final 5m of ethernet cable? Or is that ridiculous?

Although the outbuilding is 80m away, that's in a straight line. The cable can't be laid straight, so the length needed would be pretty close to 100m.

Also, what percentage of speed would I expect to lose over that distance?

Many thanks in advance for any advice.

[gg30340 · Accepted solution]

Just run the cable as one piece. More connections more loss. 

In normal use at that length you will probably not notice any drop in speed without using a speed test unless you are a heavy user doing a lot of streaming.

https://www.cablematters.com/Blog/Networking/how-long-can-an-ethernet-cable-be#:~:text=Ethernet%20Ca....

[countrypaul]

If the route you need to take works out much longer than 100m and you are concerned about whether it will work or not then fibre optic cable is an option. Obviously much more expensive (about £1/m for external steel reinforced, already terminated lengths of 150m from the big river co.), you will need a converter on each end (TP ethernet to fibre ethernet around £20 each). Much more care needed when installing, but it should be much more reliable. Have a look round at prices - I only looked at the first one I found. 

[WSH]

Yes, it is the all up total, including any patch leads from the socket to the device.

The spec is for 100m but that is a perfect install under laboratory conditions.  Most working techs don’t push it beyond 80-85m.  That having been said, it doesn’t just stop working at 101m, of course.  What happens is the error rate goes up and the speed goes down.  Depending on what you are expecting from it, you might not even notice.

I don’t ordinarily recommend Cat 7 as it’s spec’ed for 10Gb/s and way over the top for a domestic installation but in this case it might be appropriate.

[Brett-L]

Many thanks for this, it makes total sense. The linked article answers loads of questions too... thank you.

[Brett-L]

Thank you for this. I hadn’t considered a fibre option because I thought it was much more expensive to terminate at either end. It would certainly remove any concerns about cable length. I’ll def look into it.

[WSH]

Be aware that fibre needs a much bigger bend radius and has a much lower pull weight.