Breaking the law! Violating Ethernet Cable 328 Foot Length Limitations

Written by Don Schultz, trueCABLE Senior Technical Advisor, Fluke Networks Copper/Fiber CCTT, BICSI INST1, INSTC, INSTF Certified

While it’s always a good idea to avoid breaking Ethernet cable length limitations, sometimes you just have to do it. Once you’ve reached the maximum length for Cat5, Cat6, or any other cable type, you don’t have a choice. Getting from point A to point B simply won’t work unless you break all the rules!  

Case in point:  You just bought a nice house on a big piece of land.  Your driveway has a gate control at the end which allows for opening and closing at the press of a button.  There is only one problem...that gate is located 380 feet away from your powered Ethernet switch.

So, you started investigating whether you could get away with this.  Likely, if you ended up at the trueCABLE website, you read Maximum Ethernet Cable Length.  Uh oh.  That blog said you cannot go any further than 328 feet.  Your hopes are dashed.  Get those shoes on since you will be walking to that gate now (uphill both ways and through snow to be sure)!

...or will you?

This article will focus on just how far you can go with Ethernet, have it still work at levels sufficient for your needs, while breaking the formal rules. If you feel constrained by tried-and-true Ethernet cable length limitations, you've come to the right place.

There are two primary ways to go about this, depending upon the distance you wish to go:

• First up, we will talk about the way where you buy extra stuff and don’t actually break any rules 
• Second we will talk about actually breaking the rules and find out, with very extensive testing under certain conditions, just what you can get away with

A few terms and conditions, though, and please don’t skip this:

• This blog assumes temperatures are at 70 degrees Fahrenheit and below--yes temperature affects your length.  See Temperature's Effect on Ethernet Cable Length for more about that.
• If you are direct burying your cable, then you must use the correct cable jacket.  See Selecting the Correct Outdoor Ethernet Cable.
• You must use solid copper conductor Ethernet cable.  No factory pre-made stranded copper conductor cabling is allowed.  Frankly, stranded copper conductors royally suck for data transmission over distance.  See Solid VS Stranded Ethernet Cable for why.
• You have no intention of actually “Certifying” your install to the formal ANSI/TIA 568 2.D rules: Because if you try, it won’t pass I assure you.
• All terminations are RJ45 plugs, at both ends.  The cable in this instance, while being solid copper, is essentially functioning as a long patch cable.  This is called “patch as the channel.”
• All cable and termination accessories used are trueCABLE brand. Sorry folks, I cannot guarantee this will work with any other brand.

Option 1:  Buy a PoE Extender

This is really quite straightforward, but you will need to purchase the correct equipment.  The idea is to use cable from your primary Ethernet switch that has PoE (DC voltage injected across it) to power up a remote PoE powered switch.  From that remote PoE powered switch you then “renew” the signal to your final destination.  This option does not actually break any formal rules, although it is not specifically addressed in the ANSI/TIA 568 standard either.

Primary advantages to this method:

• Ambient temperature plays an important role, but just obey the temperature schedule found in Temperature's Effect on Ethernet Cable Length for any one segment and you will achieve success
• This method is tried and true, and there is specific equipment that lets you achieve your goals
• This method allows you to use any solid copper Ethernet cable Category, and works in indoor or outdoor scenarios equally well assuming you are using the right cable jacket
• You can go a long distance...up to 600 feet in the below example...and potentially to multiple devices!

Primary disadvantages:

• Will cost more
• Requires more research

How this looks, conceptually:

For example:

• The full run needs to 450 feet from primary Ethernet switch located in your house to the remote surveillance camera
• Your primary Ethernet switch is capable of transmitting high powered PoE such as PoE++ 802.3bt 60W
• Your secondary PoE powered Ethernet switch receives the power and signal from one cable, and then re-transmits the same signal along with lower powered PoE (say 802.3af/at) along another cable segment to your end point device
• The first segment and second segment should be equally 225 feet apart with the PoE extender in the middle if possible.  In the event you cannot get the remotely powered PoE extender directly in the middle of the entire run, try and keep any one cable segment below 300 feet.  This will greatly increase your odds of getting a good signal.

A couple items to keep in mind:

• All PoE hardware (primary Ethernet switch and remote PoE powered switch) needs to work and play nicely together.  I recommend purchasing the same brand, and make sure the equipment will do what you want it to.  
• At this moment, trueCABLE does not have any formally tested recommendations.  You will be on your own when shopping for this extra hardware.  Check out the Ubiquiti Networks site for equipment that may meet your needs.  Alternatively, Amazon is a potential source.  Research carefully.

Option 2:  One Long Run

Sometimes buying a remote PoE extender is not within your budget.  Perhaps you don’t need to go all the way to 500 feet.  There is a solution if your needs are more modest:  Break the rules.

This data is valid for climate controlled indoor or direct burial only conditions.  Alternatively if you live in an area that never gets above 70 degrees Fahrenheit then my condolences, but on the bright side you can ignore this rule.   I will be expanding this blog in the future to account for higher temperatures.

Most importantly, this is at your risk.  I did my part in extensive testing to bring this data to you, but we really are breaking the rules here and I cannot watch over your shoulder as you install your cable so ultimately any installation malady that causes ...a problem… is on you.

Test conditions:

• I tested unshielded Riser rated cable
• Cat5e, Cat6, and Cat6A were all tested
• Terminations were RJ45 unshielded connector plugs at both ends of the cable
• A Fluke DSX-8000 was used to conduct bandwidth tests and then finally more formal ANSI/TIA Channel tests
• Cables were tested starting at 500 feet, using 100BASE-TX (100 Mb/s speed) with 802.3bt (PoE)
• If a test passed at a certain length, the next toughest test was used until it passed as well.  This continued until the cable passed TIA Channel testing for the Category of the cable.
• The cable was reduced in length 25 feet after each failure
• The ambient temperature was 70 degrees F
• The cable was not installed, and only loosely coiled.  No sharp bends or turns were taken.

The data:

This is for 100BASE-TX + 802.3bt PoE.  This graph may be used if your end point equipment like a gate control or PoE camera only needs PoE and 100 Mb/s bandwidth.  That is frequently the case, and why this data is presented first.

Well, now this is interesting.  As it turns out, the Category of the cable is not the determining factor when trying for usable bandwidth at long lengths.  Copper diameter (expressed in AWG) is.  The smaller the AWG number, the thicker the conductor.  Our Cat6 and Cat6A cables all use 23 AWG copper conductors.

Time for a second round, this time at 1000BASE-T + 802.3bt PoE.  This graph may be used if your end point equipment needs 1 Gigabit bandwidth with PoE.  

The plot thickens.  1 Gigabit (1000BASE-T) is far less forgiving.  It is interesting that Cat6A did not do as well as Cat6 in this 1 Gigabit test.  I ran another test...that being 10GBASE-T (10 Gigabit) on the Cat6A again at 350 feet for a sanity check and it passed where the Cat6 failed at that speed and distance.  Go figure.  That just illustrates that electrical impulses get weird over long distances, and cable reliability gets a bit unpredictable.

So...I recommend keeping your maximum distance to 350 feet for 1 Gigabit regardless of Category and don’t push it!  

An interesting final test result...all Categories passed TIA Channel testing at 350 feet.  This type of test covers any bandwidth the cable Category is capable of supporting according to the standard.

Some final conclusions.

• For 100 Mb/s, use Cat6 or Cat6A if you want the best length.  You can get up to 425 feet!
• For 1 Gigabit, it does not matter what Category you use, you are limited to 350 feet.  375 feet is iffy, and if you are using PoE powered devices I would recommend not trying it.  You could short out equipment.  
• Conductor gauge is the all important factor in how far you can go
• When in doubt, always use the thicker conductor!

Well, again I have dropped a lot of information on you. Remember, violating ethernet cable 328-foot length limitations should only be considered when you’ve exhausted all other options. The topic is actually a pressing one, as many people find themselves in a tough situation where they need to stretch lengths further than the TIA standard allows. This clarifies a great deal!

HAPPY NETWORKING!

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