Cat 6 RJ45 UTP End-Open Modular Plug

For copper Ethernet, the maximum channel length from the switch to the device is 100 m, and it is the same for Cat5e, Cat6 and Cat6A at the speeds each category is designed for (for example, 10 Gbps over the full 100 m needs Cat6A). TIA-568 and ISO/IEC 11801 split these 100 m into at most 90 m of fixed cable (the permanent link, from the patch panel to the outlet) plus at most 10 m of patch cords in total at both ends. Cords lose more signal per meter, so their share must not be added to the fixed cable: 85 m of fixed cable plus two 3 m patch cords is fine, but 95 m of fixed cable is not. Measure the length along the real cable route, including rises, drops and service loops, not the straight-line distance on the drawing; PoE has the same limit.

Structured cabling is a standardized star layout: every outlet or camera gets its own permanent cable, with no splices or taps, back to a patch panel in the rack, and the racks are linked by copper or fiber backbone cabling. The main references are the ANSI/TIA-568 series (USA), ISO/IEC 11801 (international) and EN 50173 (Europe), which define cable categories, maximum lengths and test limits. They are supported by TIA-569 for pathways and spaces, TIA-606 for labeling and documentation, TIA-607 for bonding and grounding, and ISO/IEC 14763-2 or EN 50174 for installation practice. The result is one shared infrastructure for data, IP phones, cameras and PoE, in which every link can be tested individually and equipment can be replaced without re-cabling.

There are three standard solutions. Put a switch (for example an industrial PoE switch in a weatherproof enclosure) part-way along the route so that each segment stays under 100 m; use a PoE extender, which regenerates the signal and adds up to about 100 m per unit but uses part of the PoE power itself, so check what is left for the device; or run fiber with SFP modules or media converters, which covers kilometers. Some PoE switches also have an Extend mode for a single camera (about 250 m at a reduced speed, typically 10 Mbps), which is not standard Ethernet. Stretching a copper cable beyond 100 m because it worked on the bench usually ends in CRC errors, links that fall back to 100 Mbps and PoE cameras that reboot.

At 100 Mbps it is technically possible, because 100BASE-TX uses only two of the four pairs (pins 1, 2, 3 and 6), and some installers use a special splitter to give the other two pairs to a second device. It is not recommended: the link falls outside the standard and cannot be certified, gigabit (which needs all four pairs) and standard PoE for both devices become impossible, and both devices are limited to 100 Mbps. The correct solution is a second cable or a small switch, preferably PoE, near the devices; while the cables are being pulled, adding a spare one costs little.

The three categories differ in the frequency they are specified for, and therefore in their margin against crosstalk and noise: Cat5e up to 100 MHz, Cat6 up to 250 MHz and Cat6A up to 500 MHz. In practice Cat5e is built for 1 Gbps (and 2.5 Gbps) up to 100 m, Cat6 carries 1 Gbps with more margin and 5 Gbps up to 100 m, and Cat6A is made for 10GBASE-T over the full 100 m; on Cat6 a 10 Gbps link is only supported up to roughly 37 to 55 m. Cat6A is also thicker and stiffer (typically 7 to 9 mm in diameter against about 6 mm for Cat6) and takes more room in conduits and trays. In ISO/IEC 11801 terms, the channels of these categories are called Class D, Class E and Class EA.