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Using GLC-FE-100FX or GLC-GE-100FX?

Oct 19th 2015 at 1:18 AM

GLC-FE-100FX and GLC-GE-100FX are two types of Cisco 100BASE-FX SFPs. They are both interoperable with industrywide interfaces compliant to the IEEE 100BASE-FX standard. Some people are usually confused about these two modules. This article may tell you the differences between them and how to choose the right one from them. Before cutting into the theme, let’s introduce the IEEE 100BASE-FX standards firstly.

IEEE 100BASE-FX Standards
100BASE-FX is a version of Fast Ethernet over optical fiber. It uses a 1300 nm near-infrared (NIR) light wavelength transmitted via two strands of optical fiber, one for receive (RX) and the other for transmit (TX). Maximum length is 412 metres for half-duplex connections, and 2 kilometres for full-duplex over multi-mode optical fiber. 100BASE-FX uses the same 4B5B encoding and NRZI line code that 100BASE-TX does. 100BASE-FX should use SC, ST, LC, MTRJ or MIC connectors with SC being the preferred option. 100BASE-FX is not compatible with 10BASE-FL, the 10 MBit/s version over optical fiber.

Differences Between GLC-GE-100FX and GLC-FE-100FX
The Cisco 100BASE-FX SFP operates on ordinary multimode fiber-optic (MMF) link spans up to 2 kilometers (km) long. Cisco GLC-FE-100FX modules operate in Fast Ethernet or dual-rate Fast/Gigabit Ethernet ports of Cisco switches and routers. Cisco GLC-GE-100FX modules operate in Gigabit Ethernet ports of Cisco switches and routers. The difference between them is that Cisco GLC-GE-100FX operate on Fast Ethernet ports while Cisco GLC-FE-100FX operate on Gigabit Ethernet ports. Shown as the picture below: above one is Cisco GLC-FE-100FX and the below one is Cisco GLC-GE-100FX.


Which One to Use?
Although you learn about the differences, you may also think all SFP ports on switches were Gigabit ports and thus the GE version would be needed for 100fx connectivity. Then, which switches would you use each SFP in? In particularly, which ones to use in a 2960-24PC-L switch and a 3560-8PC switch.

In fact, if you look closer at that compatibility matrix that FE is for 100BASE-FX SFP module for 100-MB ports and the GE is for 100BASE-FX SFP module for Gigabit Ethernet ports. Not all SFP slots are Gig. For the 3560-8PC switch, the compatible SFPs are Cisco GLC-FE-100FX, GLC-FE-100LX, GLC-FE-100BX-D, GLC-FE-100BX-U. And for the 2960-24PC-L switch, Paulo stated that all of the 100FX SFPs are compatible.

Besides above, you may also doubt that if all kinds of 100FX SFPs are compatible for 2960-24PC-L switch, then which one is performing the best. The answer id that if your switch is 10/100/1000 then you can run a GE SFP, but if your switch is 10/100 then you can’t run a GE SFP. The 2960 you get will be either GIG capable on the uplink or not.


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