Ethernet Cable Max Distance - Something to Think About

samplenhold

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There have been a lot of threads about maximum distance lately and also posts in existing threads discussing this issue. Now everyone seems to state 100 meters. But I was thinking about this and decided to do a little investigation.

The reason for this is a situation where the 'final destination' of the video signal would be much more than 100 meters from the cam. So I was trying to understand the 100 meter rule. Is that the total distance from cam to NVR (or BI PC)? Or is that the distance between one piece of networking equipment to the next?

I was thinking that I could put a few cams in an area and they would be connected to a POE switch. Call that a 'satellite group'. Those runs maybe 30-40 meters from each cam to the satellite POE switch. Then run an ethernet cable from that satellite switch to a second switch that is in a central location 100 meters from the satellite POE switch. Call that the 'central switch'. The install might need three or four of these satellite groups all running back to the central switch. From that central switch to the NVR/BI PC is maybe 5 meters. So a total max distance from cam to NVR would be about 145 meters. But the maximum distance from one switch to another would be 100 meters.

So in researching this I found some posts on the Cisco Community where back in 2015 someone asked a question very similar to this. About every answer to the post stated that the 100 meter max is between switches, not the full path. Now it gets interesting due to a 'late post' from September 2019 (4 years after the last post in the thread), cut and pasted below:

The 100M limitation is dated information. Back when we used hub and only had half-duplex. Because of half-duplex, you had to transmit and receive on the same wire. The 100M distance was a restriction because that was the amount of time took for the packet to be physically transmitted and arrive on the remote side of the cable to avoid collisions before the remote side to transmit.

If you use full-duplex, which we should be by now (even when this was posted in 2015)... you can easily get 500 feet from Cat5/6. We do this every day with brand spankin' new Cisco APs (which run over POE).

Also, a patch panel is not a repeater unless there is something in the patch panel electronically retransmitting the packet (repeater)

Sorry for the late arrival but I was looking for something to quote for this same topic and found this incorrect answer.



So I do not have the networking knowledge/experience to know if this is correct or not. Can anyone with the appropriate knowledge/background give their viewpoint on this?

P.S. the comment WRT "a patch panel is not a repeater" was in reference to someone stating "good patch panels can act as repeaters as well to regenerate layer 1 signals breaking the 100m issue". in the tread.
 
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not sure about meters :) 320'ish feet is the max distance "recommended" to go over cat5/cat5e/cat6 and most likely future cat's. It's all about electricity and network signal distance. I have slapped in warehouse AP's over 400 foot runs of Cat6. However, packet loss was evident. The AP ran hand held bar code scanners so was ok to use. Would work super slow on a laptop/smartphone.
Yes, you can connect switch > 320 feet of network cable > switch > 320 feet of network cable > switch...etc. We have had customers who have various network cabinets using only Cat6 instead of fiber that do this kind of spider webbing. You can not (well, sure you could but results are unpredictable) switch > 500 feet > switch > 500 feet...etc.
Total distance for networking protocols (IP) is 328 feet from one electrical networking device to the next. So if you have a 30' patch cord -> faceplate/jack -> 328' Cat6 -> patch panel -> 15' patch cord -> switch... you are over the 328' total length since you have to include the copper in the patch cords.

The person giving out 500' easy distance is 100% wrong and is bad information. Unless the person was running dumb terminals or hand held bar scanners.
And it's not "video signal" of more than 100 meters. It's computer network digital IP protocol.
 

IAmATeaf

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The switch also plays an important part, as it drives the wire/signal. I’ve had crap switches that refused to maintain a reliable connection on a cable length of only 25m. After a lot of head scratching, replacing the switch resolved the issue.

So all in all a lot of variables. I too have read about switch to switch to increase the max distance of copper cabling but don’t think I’ve ever seen it used in real life as most cablers will insist at using fiber instead.
 

biggen

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The problem is you aren't guaranteed to get functional ethernet out past 100m. I for one don't want to go to the trouble of building out a network and running cable past 100m on the off chance it might work. I only want to go through all that trouble knowing it will work.
 
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I used to do a LOT of installations, turnkey style. We supplied TDR traces for every drop. Every now and then a situation would crop up where the drop was more than 100 meters from a switch no matter how "creative" we could be. I've TDRed drops out at 500 feet and they do work, but keep in mind we used Cisco equipment exclusively so the quality was there at the switch end. We never looked at packet losses, but they had to be there because speed was definitely slower on a drop like that. I'd be comfortable at 400 feet, but no further and definitely wouldn't have a switch loaded with over length runs like that.
 

DsineR

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True, but more than what's needed for a typical camera.
Ex. 1080p camera, h.264 high quality, 30fps needs 4.5Mb/s.
 
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Dahua adopts advanced 2D-PAM3 coding modulation from physical layer, and realizes full duplex transmission over 800 meters at the speed of 10Mbps, or 300 meters at the speed of 100Mbps via Cat5.
I never read up on how ePoe works but now I kinda see. A Dahau only patent special algorithm to connect a Dahua ePOE IP camera long distance to a ePoe NVR. At 800 meters, max speed would be 10Mmbs.
Though would love to test, I believe it can be done. However, do notice is only setup between dahua nvr & camera. Not linkysys switch to linksys switch. And at 800 meters, only 10Mbps (great for a single camera or two).
* edit *
I stand corrected. Dahua does make a stand alone ePoe switch. So I wonder if you can do dahua switch to dahua switch. But still, the cap of Mbps of 10 is a limiting factor.
 

DsineR

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I don't believe the ePOE switches can be 'daisy-chained', but really not a selling point - 800m is a long way.
The 10Mbps cap kicks in after 300m, which as noted above is good for a typical cam. Anything under 300m is good for 100Mbps.
 

spuls

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PoLRE is a common standard for this, but I would only recommend it with (smart) managed switches. it's a bit tricky to debug such connections and with unmanaged switches it gets really tedious.

another point is the number of connections. for a handful of cameras PoLRE is a good solution. for many connections i would rather work with multiple switches for cost reasons and troubleshooting.


 

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I used to work for Cisco for over a decade. You can probably tell by some of my posts about configuring Cisco devices. I've always followed the best practice rule that the limit for copper based Ethernet (X-BaseT) using UTP cable is 100m. My recommendation is to stick to the 100m limit guidance. You can add another "satellite" switch if you want to extend the distance, but each segment max is 100m.

Some companies might come out with propriety solutions for extending distances at lower speeds (like Dahua's ePOE). When Cisco first developed POE, it was also proprietary and it eventually went through the IEEE process and became a standard. I have not heard of Dahua trying to make their implementation an IEEE 802.3 standard (doesn't mean you shouldn't use it, just means that it may never gain broad adoption by other companies).

LRE (and PoLRE) has been around for some time but speeds are also quite limited. I've seen this used for IP phone deployments, but not for IP cameras. Not saying that it can't be done.

Some history about PoE: What Is Power over Ethernet (PoE)?
 

GeoffColl

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May I pop in with a related question.

I purchased a POE camera, without much knowledge on more than the basics, on the basis of advertised max of 100 metres and installed it at the end of a CAT6 cable. The PTZ is sluggish and the signal is mostly stable, prone to drop out when there's windy conditions and vegetation movement - camera support have since advised the max should be 70 metres! Och weel.

Which degrades over distance more quickly, power or signal? For instance if I was to add a wifi AP to bring the signal home, would there be enough power in the CAT6 to work both the transmitter and the camera to provide a more stable signal? The alternative, of course, would be to power out part way and put in shorter cables - which might be more sensible, but as I've already installed the CAT6.....
 

biggen

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I'd think if your having problems now, then adding another device to power at the other end would probably make things worse not better.

I'm a little surprised you are having issues out to the 100 meter though. You may want to cut off those RJ45 jacks and re-crimp them. You may have a loose or poor connection.
 

GeoffColl

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I'd think if your having problems now, then adding another device to power at the other end would probably make things worse not better.

I'm a little surprised you are having issues out to the 100 meter though. You may want to cut off those RJ45 jacks and re-crimp them. You may have a loose or poor connection.
OK - worth thinking about. Most of the time things are ok, it's just when it's windy signal suffers. If having an AP bridge is likely to make it worse I'll have to live with or consider alternative.

How long is the cable from the switch to the camera?
It's 100 metres switch to camera - assuming the manufacturer measured it correctly :D - 2 metres switch to router.
 

biggen

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Something is loose if you are losing signal only during windy conditions. At least, that is what I would think.

If you are using pre-built Cat6 then re-crimping connectors may be out of the question. They normally use stranded conductor on those pre-built cables.
 
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The first thing I'd do is get the PC connected directly to the switch and not got through the router. Consumer grade routers have limited backplane bandwidth capabilities which can cause the problem you are seeing. I'm not saying it is the cause, but it easily could be and it's worth testing to see if it helps.
 
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