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I wonder how many "jacks" are allowed for running copper (Cat6a and Cat7) link for 10GbE connections.

Questions is pretty simple but I am confused about "link segment" term. From specification it seems that Cat6a/Cat7 rated for 10GbE on up to 100m for single link segment. Does it mean that we can have 10GbE on 100m cable between switch and computer, or we can have patch panel in the middle (so that it is 100m switch->patch panel plus 100m panel -> computer)?

My guess is that "link segment" means cable between active components, not jacks.

Here are details on the spec for cat6a and cat7, and here link segment is defined.

PS: Question comes from our new building where 10GbE over cat6a cable is promised, however I don't see how it can possibly satisfy requirement for 100m straight line of cable.

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    A copper cable channel has three sections between active devices. The horizontal cable is up to 90 meter of solid-core cable, and the work area cord and patch cord, both of which are stranded cable, and total no more than 10 meters, giving you up to 100 meters in the channel. – Ron Maupin Nov 30 '17 at 3:20
  • @RonMaupin thats what i understand. However, AFAIK, every turn of the cable along the wall will rob reliability/bandwidth, right? – aaaaa says reinstate Monica Nov 30 '17 at 5:25
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    Well, the standard takes into account such things. For example, there should be a 10' service loop at each end of the horizontal cable. There are things like the maximum pulling tension and minimum bend radius, and if you exceed those in installation, you can permanently ruin the cable. A certified installer will use a (very) expensive tester (many thousands of dollars) to run the full category test suite on each cable installed, and he will provide you with a full report of each test in the suite for each cable installed. He will correct any problems and retest. – Ron Maupin Nov 30 '17 at 5:53
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    Look at my answer to this question for the primary tests. The exact pass/fail test values depend on the cable category. Also, the cable works at a specific speed for a standard, e.g. 10GBASE-T for 10 Gbps ethernet on UTP, or it doesn't support the standard at all. You will not get a speed lower than 10 Gbps for 10 Gbps devices on the cable. The cable may work with 1000BASE-T, 100BASE-TX, or 10BASE-T, but you will not get a speed between any of the specific speeds because of the cable. It either works at a speed, or it doesn't. – Ron Maupin Nov 30 '17 at 6:05
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My guess is that "link segment" means cable between active components, not jacks.

This is correct. You need a device that will terminate and retransmit (not just amplify) the ethernet frame. This is so collision detection from the signal originator will function properly.

When sending an ethernet frame, the transmitter listens for a specific period to make sure there was no collision with another transmitter. If the cable is longer than the specification, it's possible for a collision to happen after the transmitter stops listening and fail to detect the collision.

This means "powered" alone isn't always enough. It's usually safe, but it is possible to get a powered hub that's still part of the same segment. However, a switch should always be okay, and a bridge (in the formal networking meaning) should always be okay.

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  • The 10 Gb ethernet standards have removed half duplex, leaving no possibility for collisions. – Ron Maupin Nov 30 '17 at 3:21
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To me, a link segment has always been between two powered devices (switch, router, PC, hub, repeater, bridge- take your pick). A patch panel would not be included in this as a patch panel is not powered. You have 100 meters per a single powered segment (100 meters between switches, from switch to computer, etc).

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A link segment is a connection between 2 active devices. For example if you put a swtich in the middle you will have 100m to one computer and another 100m to the other computer making total distance 200m

If you put 2 Switches you can have 100m to first switch plus 100m between switches and another 100 to the other computer making 300 mts...

It is not advisable to stack more than 4 switches. so this gives you around 600m in UTP

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