Ethernet Cable & Standards Reference
Copper category ratings, Ethernet standards with real reach limits, and the T568B pinout - the physical-layer facts you need on site.
Result
Copper categories
| Category | Bandwidth | Supports | Reach | Notes |
|---|---|---|---|---|
| Cat5 | 100 MHz | 100BASE-TX (100 Mbit/s) | 100 m | Obsolete. Not rated for gigabit. |
| Cat5e | 100 MHz | 1000BASE-T (1 Gbit/s) | 100 m | Still ubiquitous. 2.5GBASE-T often works to 100 m in practice. |
| Cat6 | 250 MHz | 1 Gbit/s to 100 m, 10 Gbit/s to 55 m | 100 m / 55 m | The sensible default for new copper installs. |
| Cat6a | 500 MHz | 10GBASE-T (10 Gbit/s) | 100 m | Required for 10G over the full reach. Thicker and less flexible. |
| Cat7 | 600 MHz | 10 Gbit/s | 100 m | Shielded, uses non-RJ45 connectors in its original form. Largely bypassed by Cat6a. |
| Cat8 | 2000 MHz | 25/40GBASE-T | 30 m | Datacentre top-of-rack only, limited to short runs. |
Ethernet standards
| Standard | Rate | Media | Requires | Reach |
|---|---|---|---|---|
| 10BASE-T | 10 Mbit/s | 2 pairs | Cat3+ | 100 m |
| 100BASE-TX | 100 Mbit/s | 2 pairs | Cat5+ | 100 m |
| 1000BASE-T | 1 Gbit/s | 4 pairs | Cat5e+ | 100 m |
| 2.5GBASE-T | 2.5 Gbit/s | 4 pairs | Cat5e+ | 100 m |
| 5GBASE-T | 5 Gbit/s | 4 pairs | Cat6+ | 100 m |
| 10GBASE-T | 10 Gbit/s | 4 pairs | Cat6a (Cat6 to 55 m) | 100 m |
| 1000BASE-LX | 1 Gbit/s | single-mode pair | 1310 nm SMF | 10 km |
| 10GBASE-LR | 10 Gbit/s | single-mode pair | 1310 nm SMF | 10 km |
| 10GBASE-ER | 10 Gbit/s | single-mode pair | 1550 nm SMF | 40 km |
| 25GBASE-LR | 25 Gbit/s | single-mode pair | 1310 nm SMF | 10 km |
| 100GBASE-LR4 | 100 Gbit/s | single-mode pair | 4 × CWDM | 10 km |
T568B pinout
| Pin | T568B colour | Function | Pair |
|---|---|---|---|
| 1 | White/Orange | TX+ (BI_DA+) | Pair 2 |
| 2 | Orange | TX- (BI_DA-) | Pair 2 |
| 3 | White/Green | RX+ (BI_DB+) | Pair 3 |
| 4 | Blue | BI_DC+ | Pair 1 |
| 5 | White/Blue | BI_DC- | Pair 1 |
| 6 | Green | RX- (BI_DB-) | Pair 3 |
| 7 | White/Brown | BI_DD+ | Pair 4 |
| 8 | Brown | BI_DD- | Pair 4 |
About Ethernet Cable & Standards Reference
The physical layer is where a surprising share of network faults live. This collects the category ratings, the standards with their actual reach limits, and the pinout - the facts worth having to hand when a link is up but throwing errors.
Diagnosing physical-layer faults
A link that comes up but errors is almost always physical. Check the negotiated speed and duplex first — a link that fell back to 100 Mbit/s half duplex on gigabit hardware usually means a broken pair. Then look at CRC errors, which indicate corruption in transit, versus input errors and late collisions, which point at length or duplex mismatch. A cable tester that only checks continuity will pass a cable that fails at gigabit, because it never measures crosstalk or return loss.
Cat6 or Cat6a for 10G
Cat6 supports 10GBASE-T only to 55 m, and less in a dense bundle where alien crosstalk between adjacent cables becomes the limit. Cat6a is rated for the full 100 m. If a run might carry 10G within its lifetime, the incremental cost of Cat6a at install time is far smaller than re-pulling it. Beyond that, fiber is usually the better answer than Cat8.
Common use cases
- Choosing a cable category for a new install.
- Checking whether an existing run will support a 10G upgrade.
- Terminating a patch panel or field-fitting a plug.
Edge cases and gotchas
- CRC errors and late collisions usually mean a physical problem: length, a bad termination, or a damaged pair.
- Do not exceed 25 kg of pulling tension or bend cable tighter than four times its diameter - both permanently degrade performance.