When renovating a home we pre-bury Ethernet cables, and we also buy some in daily life, but the market is a mess — Cat5e, Cat6, Cat6a, Cat7, even Cat8 and Cat9. How not to get ripped off by shady sellers? Today I’ll explain how to choose Ethernet cables.
Ethernet Cable Categories
First, where the categories come from. They come from ISO/IEC 11801 (Information technology — Generic cabling for customer premises), written and maintained by ISO/IEC JTC1 SC25. As of 2019-10-23, the IEC 60603-7 connector standard and IEC 61156 twisted-pair standard are as follows:
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CAT1: cable and connectors supporting bandwidth up to 100 kHz
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CAT2: cable and connectors supporting bandwidth up to 1 MHz
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CAT3: cable and connectors supporting bandwidth up to 16 MHz
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CAT5 (also called Cat 5e / Cat5e): cable and connectors supporting bandwidth up to 100 MHz
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CAT6: cable and connectors supporting bandwidth up to 250 MHz
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CAT6A: cable and connectors supporting bandwidth up to 500 MHz
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CAT8.1 (draft, also called Category 8 by TIA): cable and connectors supporting bandwidth up to 2000 MHz within 30 meters
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CAT7: cable and connectors supporting bandwidth up to 600 MHz
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CAT7A: cable and connectors supporting bandwidth up to 1000 MHz
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CAT8.2 (draft): cable and connectors supporting bandwidth up to 2000 MHz within 30 meters
Note: the larger the physical bandwidth, the higher the supported transfer rate.
The Most Common Ones in Daily Use: Cat5e, Cat6, and Cat6a
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Cat5e: transmission frequency 100 MHz, mainly for gigabit Ethernet (1000 Mbps)
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Cat6: transmission frequency 250 MHz, best for applications above 1 Gbps, mainly gigabit Ethernet (1000 Mbps)
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Cat6a: transmission frequency up to 500 MHz, double that of Cat6, mainly for 10G (10 Gbps) networks; labeled “CAT.6A” on the jacket, and it supports 10G Ethernet with a “10Gigabit” mark on the appearance
Conclusion of this section: for 100M networks use Cat5e, for 1G use Cat6, for 10G use Cat6a.
The Other Ones: Cat7, Cat7a, and the Cat8/Cat9 Sellers Mention
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Cat7: transmission frequency up to 600 MHz, performance close to Cat6a; pure-copper 8 cores with a shield layer, stronger overall; transfer rate up to 10 Gbps, used in data centers and similar settings.
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Cat7a: transmission frequency 1000 MHz; Cat7 and above fully support 10G networks.
Shielded or Unshielded
Shielded cable adds an aluminum-foil or braided-metal shield on top of unshielded cable; because of the shield, it resists external interference strongly. In high-interference environments, shielded cable is more stable and secure.
But shielded networking has very strict installation requirements: the whole system must be shielded, including RJ45 plugs, jacks, and switches. If any single part isn’t shielded, the whole system loses its shielding effect. And the shield needs a good grounding system, through which interference current is directed to earth.
So in a home environment there’s no need at all for shielded cable, since you basically can’t meet the shielded system’s installation requirements at home.
Conclusion
For home wiring and daily use, Cat6 and Cat6a are more than enough, and you don’t need shielded cable — so plugs, jacks, and switches don’t need shielding either. 10G gear is still pricey; except for a few enthusiasts, ordinary users are fully covered. Sellers who talk you into expensive Cat7-and-up shielded cable aren’t trustworthy — in reality you can barely build a complete shielded system.