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When putting Ethernet cables for an office there are two ways to put the cables:

  1. From the rack patch panel a cable to each end-point (workstation).
  2. From the rack patch panel a cable to each room/floor switch, and from the switch another cable to the end-point (workstation).

About distances, from rack to the more far room there are near 100 meters. Inside a room no more than 15 meters.

We prefer the second option because is cheaper but no sure about performance issues.

Any suggestion? Thanks!

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4 Answers 4

up vote 6 down vote accepted

If the cabling is done right, there will not be any performance issues.

Signal traveling speed on copper media is approx 2/3 the speed of light. That's 200.000Km/s. Let's just say a few extra hundred meters are not going to matter.

I think option 2 is indeed the best and that's what I have seen deployed just about everywhere I've been.

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Another reason to go with option 2: Limiting damage. I've worked in a few buildings with major static issues and seen switch ports (and entire switches) fried when someone plugged/unplugged. Better that happen to a small floor/room switch than losing a card on a datacenter switch :-) –  voretaq7 Feb 16 '10 at 16:27
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Also As you grow an "option 3" comes up: Rack -(fiber)-> Floor switch -(copper)-> Floor patch panel -(copper)-> End-point. Option 2 sets you up for that nicely :) –  voretaq7 Feb 16 '10 at 16:30

It will depend on your size. If you only have a hundred or so users imho it would be better to wire things all back to the central patch panel and do your switching from there. This is mainly a security of infrastructure question in my mind as it's a lot easier to lock a comms room and have your switches away from prying hands.

If your talking multiple hundreds of users then wiring them back to floor or department comms rooms which are locked and then trunking the traffic back to your primary comms room.

Whatever you do don't forget to leave enough dark cable to handle redundancy/expansion. You don't want a rat to eat a cable and take out an entire department.

Ultimately you need to decide based on traffic type of your users, budget etc. Managed switches throughout will also make the 2nd option more viable but personally I agree with Antonie in that switching latency is unlikely to be a huge concern.

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In a large office I'd always go for option two for the reasons already listed by Antoine and Antitribu however there is another factor to consider, there is a limit to the length of any given cable before signal degradation occurs. If memory serves for Cat5 & Cat6 cable the standard is 100m (of solid core cable) from patch panel to wall point which allows for a 10m (stranded) patch cable at either end.

In reality I've had reliable gigabit speeds from 150m cables but I wouldn't want to go much beyond that.

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It's actually 90m of in wall cable + 10m of patch cable. Total run from switch to device is limited to 100m. –  Grant May 19 '12 at 15:24

Your question was asking specifically about performance - of the two options I'd say that direct patching (option 1 - panel to workstation) would give higher performance than panel to switch to workstation.

The reason for this would be as the switch will be caching the MAC addresses associated with each switch port in order to route layer 2 traffic to the correct host. If you have a separate switch plugged in to the panel from the core switch then you will end up with twice as many lookups and ARP requests on the network.

With the wrong switch combinations I once saw (historically) a switch flooding its ports with ARP requests because its cache for a specific port was getting overloaded with the number of MAC addresses responding on that port.

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