Cable Distance

up2thetime

I can't remember where I heard/read this... but using a twisted-pair cable longer than 100m will result in late collisions?

If that is correct, then suppose we have 2 computers connected by a few switches: PC1 will have a cable of 100m to a switch, and that switch can be cabled to another switch via another 100m cable, then that switch cabled to another via a 100m cable, and finally to PC2 on yet another 100m cable. So the combined distance of cable is 400m. Why couldn't we just use (2) 200m cables and one switch rather than using (4) 100m cables and 3 switches...

PC1--100mcable--SW1---100mcable---SW2---100mcable---SW3--100m---PC2


versus

PC1----200mcable----SW1----200mcable----PC2


Maybe I'm forgetting something really basic... (perhaps this has to do with attenuation?). But if it does have to do with attenuation, then I don't see the relation between attenuation and a collision.

Thanks

Firemarshalbill.com

Looks like an attenuation problem to me. Switches create collision domains 1 per port.

Kaminsky

Copper has working distance of about 100m. (including patch panels if you use those in the circuit). You can try to go longer but 110, 120 you are really going to have problems.

In your scenario, the switch ports repeat the signal so no run would be more than 100m. If you use dumb patch panels to do that same run, the signal wouldn't get passed the first patch panel once it exceded the 100m. Routers, switches, bridges, hubs, etc all repeat the signal as they send it out so you get a fresh 0 distance as it leaves the device. This is the same for copper, fibre, etc.

Putting switch after switch after switch is a not really feasable. Doubt you would have wiring closets every 100m in that route as well. If you need to cross that distance, get some fibre in there and use media converters to switch from copper to fibre and then back again at the other end. Whether the intermediary fibre is done by cablers, panel to panel or you get hold of a pre-terminated 410m length of multimode and run it yourself would be upto what you can afford and what growth you expect.