I need to run an ethernet cable to another room which is more that 100m away.

My internet guy just told me that CAT5 ethernet cable range is 100m. He stated that it does not make a difference if we connect switch in between like 50m cable, switch and another 50m. He said that the length accumulates.

I think he is wrong about that. However, if I am right that switch can actually extend ethernet cable.

Then for each switch we can begin another 100m of ethernet cable? If so we can technically do this forever? Beside using switch should I get some other specialized device to accomplish this instead?

  • You may want to look at this Spiceworks forum post. – Anaksunaman May 18 '18 at 7:47
  • Alternatives to using a switch include using fibre which can easily get you 5 kms without really trying, way, way more depending on the type. (Comment brought to you thanks to the Southern Cross fibre cable linking AU and NZ with USA) – davidgo May 18 '18 at 9:15

The length restriction is related to collision detection.

As each switch port is a collision domain, you can use a switch to extend the distance and get more than 100m.

Just like this :

A ------------------------Switch ----------------------------B 

           100m                                100m

You can continue extending the distance using another switch from B to another destination and so on, however it is recommended no extending more than 7 switches (7 hops).

The 7 hops limitation is related to the Spanning Tree Protocol. This protocol is designed to control and prevent the creation of closed loops in a switching network.

In a case where you will need to use 7 or more switches, then it's better to put some fiber optic from initial source to final destination and use only one switch.

  • Hi thank you! Is switch a good device to do what I am doing? I have read "Placing Ethernet extenders at intervals along your cat 5 cable runs can greatly extend the reach of your network. The most powerful Ethernet extenders can extend your network out as far as five miles. ". Should i use switch or ethernet extender? – Zanko May 18 '18 at 7:50
  • 1
    @Zanko Ethernet Extender is a device that does an electric conversion of the signal to make it possible to get long distance. They are oriented to cover big distances and therefore they are more expensive than a home switch. For a solution as getting to the next room is better to use a switch. – jcbermu May 18 '18 at 7:57
  • Umm, the 7 hop limitation is for layer 2 Spanning tree convergence. It has nothing to do with consumer grade switches, thus they do not have this limitation. The simple answer was, at layer-1 the packet gets re-transmitted out of the egress port, and the limitation is one hundred meters from each egress. – Tim_Stewart May 18 '18 at 12:25
  • Also, what makes you think a collision domain has anything to do with distance and not physical layer signaling? I smell a whole lot of b.s in this answer... – Tim_Stewart May 18 '18 at 12:51

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