10Gbe over Cat5e?

ubersonic · 18 May 2018 at 10:26

This thread is 8 months old, update at bottom.

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There seems to be a LOT of conflicting information on the net about this, Google results vary from "can't be done" to "fine up to 44 meters" so I figured somebody here may know what the score is with this.

The structured cabling I would want to reuse is solid core Cat5e (Premise/Molex Powercat 5e to be precise). Longest runs from patch to sockets are ~20 meters.

bledd · 18 May 2018 at 10:44

Should work fine, if it's decent cable and good terminations, then I think ~40-50M is the max length. We tend to use fibre for 10Gb links.

vvalter · 18 May 2018 at 10:49

Probably fine. I'd just go for it, you can always replace the cable if it doesn't work, but I'm pretty sure 10Gb over decent cable will be no problem if it's only 20 meters.

WJA96 · 18 May 2018 at 17:43

I don’t see where the confusion arises. It’s not in the 802.3an standard to use CAT5e cable with 10BaseT (10GbE) Ethernet.

The standard says that you can use CAT6 cable for run lengths up to 55m or CAT6a or CAT7 cable for run lengths up to 100Mbps.

So that doesn’t mean it won’t work, but it almost certainly means you will see more dropped packets and slower transfers than you would with CAT6 or better twisted pair cable. Anything that is operating at the ragged edge of the standard (Im thinking Broadcom/Marvell/Aquantia rather than Intel) will probably run at 5/2.5/1GbE because the controller will scale back speed to limit communication errors.

The standard is there for a reason. It GUARANTEES interoperability but that doesn’t mean that you can’t get away with something that isn’t quoted in the standard.

Habakkuk · 1 Jun 2018 at 07:56

I've been told Cat5e is usually Cat6 without the certification.

bledd · 1 Jun 2018 at 10:26

You've been told wrong. Cat6 had thicker copper.

WJA96 · 1 Jun 2018 at 13:13

And CAT6 has a big-old lump of shielding down the middle.

bremen1874 · 1 Jun 2018 at 13:15

WJA96 said:
And CAT6 has a big-old lump of shielding down the middle.

Pedantic I know, but the plastic spline isn't a shield.

WJA96 · 1 Jun 2018 at 15:34

bremen1874 said:
Pedantic I know, but the plastic spline isn't a shield.

Well, technically, no it’s not but it keeps the pairs away from each other with the express purpose of reducing interference between the pairs. So it does act as a shield. This is obviously clearer in CAT6a.

iNQUAM · 13 Dec 2018 at 12:36

WJA96 said:
... but it almost certainly means you will see more dropped packets and slower transfers than you would with CAT6 or better twisted pair cable.

Although might be technically true, this experiment seems to indicate very low error rates and/or dropped packets when staying in reasonable cable lengths with 10gbe on cat5e. In fact, the 10gbe test was better than 1gbe on the cat5e network in this instance and transfer speed was basically exactly what one would expect.

So, if you have cat5e already installed I would not run out and buy new cables as a first step. Buy the switches and stuff, test and only replace the rest if needed.

ubersonic · 12 Jan 2019 at 02:37

Quick update on this for anyone who was wondering how it resolved.

I'm currently running 10Gbit flawlessly on the Cat5e structured cabling in the building, spoke to various cable manufacturers and most seem to rate their 5e for 10Gbit up to 45 meters (as opposed to 55 meters for Cat6 or 100 meters for Cat6a and Cat7). It should be noted however that this only applies to structured cabling (the solid copper Cat5e you find in walls) not the more flexible patch leads, you would still want to use at least Cat6 patch leads with 10Gbit to avoid any potential issues.