What is the Longest Cat6 Cable You Can Run Between a PC and a Switch?

When preparing to run some new cable for your computer, it pays to know what the limitations are so that you do not experience any problems afterwards. With that in mind, today’s SuperUser Q&A post provides some helpful knowledge to a confused reader.

Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites.

The Question

SuperUser reader Bhavin wants to know what the longest Cat6 cable a person could run between a single computer and a switch is:

When I am using a “single PC to switch” setup with a VLAN function/configuration, what is the longest Cat6 cable I can use? I have read that there is a 100 meter length limitation, but I am not talking about daisy-chaining or having other users on the same line (the PC connects directly to a switch).

What is the longest Cat6 cable a person could run between a single computer and a switch?

The Answer

SuperUser contributor Ron Maupin has the answer for us:

The UTP standard, to which the various Ethernet standards adhere, is 100 meters, but that assumes 90 meters is solid-core (better performance, but more fragile) with 5 meters on each end as stranded (worse performance, but more flexible).

It has nothing to do with daisy-chaining, but with several measurements such as frequency, insertion loss, NEXT, PSNEXT, FEXT, ELFEXT, PSELFEXT, return loss, propagation delay, delay skew, balance, longitudinal conversion transfer loss, etc.

The 100 meter limit also assumes that the cable is pre-built or professionally installed with all the same rated components and checked to see if it will pass the full-test suite. Even experienced installers have problems when installing Category-6 cabling, although Category-5E cabling can do 1000BASE-T at the same distance. Category-6 cabling can do 10GBASE-T at 55 meters, but Category-6A cabling can do 10GBASE-T at a full 100 meters.

For those who are curious, there are some big equipment vendors (i.e. Cisco) that support Category-6 cabling with 10GBASE-T for 55 meters. The participants in the new NBASE-T Alliance also support 5 gigabits on Category-5 cabling at 100 meters. You can look at the documents, such asAt-A-Glance – Cisco Multigigabit Ethernet Switches (this is a direct PDF download link).

Have something to add to the explanation? Sound off in the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.