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100 Gigabit Ethernet (100GbE) is Ethernet operating at a nominal data rate of 100 gigabits per second. The term identifies a speed class—not a particular cable, connector, or optical transceiver. The physical equipment needed for a 100GbE link depends on the specific PHY, medium, reach, and endpoint compatibility.
What does 100GbE mean?
100GbE is shorthand for 100 Gigabit Ethernet: Ethernet operation at a nominal rate of 100 Gb/s. IEEE’s overview of IEEE 802.3-2022 describes Ethernet as using a common Media Access Control (MAC) specification and management information base (MIB) across selected speeds from 1 Mb/s to 400 Gb/s, with speed-specific interfaces and physical-layer devices (PHYs).
In practical terms, Ethernet’s shared MAC framework does not mean every Ethernet speed uses the same physical connection. A PHY handles encoding and decoding for a chosen speed, medium, and link length. IEEE’s overview includes PHYs for coaxial cable, twisted-pair cable, fiber-optic cable, and electrical backplanes. IEEE 802.3-2022 overview
Does 100GbE specify a cable or transceiver?
No. “100GbE” alone does not tell you which cable, optic, connector, or module to use. Those details depend on the particular PHY and equipment. For a real link, check the PHY, medium or fiber type, connector and module form factor, supported reach, and compatibility with both endpoints.
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How do 100GbE implementations differ?
These examples show why the speed label is not enough to choose link hardware. The reach figures apply only to the documented PHY or module context, not to every 100GbE link.
| Example | Medium and documented reach | What to verify |
|---|---|---|
| 100GBASE-SR4 | IEEE 802.3bm added 100 Gb/s operation over multimode fiber. IEEE task-force baseline material identifies SR4 for 100 m MMF in that baseline context. | Confirm the fiber and endpoint requirements for the specific equipment; 100 m is not a universal 100GbE or multimode-fiber reach. |
| 100GBASE-LR4 QSFP | Cisco documents a QSFP LR4 option for up to 10 km over G.652 single-mode fiber using duplex LC connectors. | Check that the module is supported by the specific switch or network adapter and that the fiber, connectors, and link reach match its specifications. |
IEEE 802.3bm amendment record · IEEE 802.3bm adopted baseline proposals · Cisco 100GBASE QSFP-100G Modules Data Sheet
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What should you check before choosing 100GbE hardware?
- Identify the supported PHY. Confirm the exact 100GbE PHY listed for the switch or network adapter; the 100GbE label does not guarantee a particular optic or cable.
- Match the medium and reach. Verify the required fiber or other medium and the maximum supported distance for the chosen PHY and module.
- Match connectors and form factor. Check the module type and connector details against both endpoint documentation and the installed cabling.
- Confirm endpoint compatibility. Consult the equipment documentation for supported modules and interoperability before connecting the devices.
The IEEE references establish the distinction between Ethernet speed and physical-layer implementation; the Cisco data sheet provides a vendor-specific module example. Specifications and product availability can change, so use the current documentation for the exact devices being connected.
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