A 100G QSFP28 optic fiber module is a hot-pluggable transceiver module with a data rate of 100G. Each lane can carry up to 28Gbps of data, as indicated by the "28." The QSFP28 has four electrical lanes that can be configured as 4x10GbE or 4x25GbE depending on the transceivers used. The main types of QSFP28 optics consist of 100G QSFP28 SR4, QSFP28 PSM4, 100G QSFP28 LR4, and QSFP28 CWDM4, as seen below.
Optical Module Type
Banded single mode
How to Run 40Gbps on QSFP28 100G Port
100G QSFP28 interface should accelerate to the comparable 40G and function with 40G QSFP+ optics if the opposing equipment uses 40G service speed.
- QSFP+ 40G transceiver with MTP/MPO connector; MTP/MPO 12 fibers trunk cable
- 40G QSFP+ to QSFP+ DAC Cable
- 40G QSFP+ to QSFP+ AOC Cable
When using QSFP transceivers in QSFP28 ports, keep in mind that you have both single-mode and multimode (SR/LR) optical transceivers and twinax/AOC options that are available.
How to Realize 4x 10GbE Mode on QSFP28 100G Port
When the new switch only has 100G ports on one side and the existing devices only have SFP+ 10G ports on the other, it is probable to use the QSFP28 port in 4x 10GbE mode using a QSFP+ 40G optical transceiver.
- QSFP+ 40G transceiver with MTP/MPO connector; SFP+ 10G transceivers with LC connector; MTP/MPO-LC harness cable
- 40G QSFP+ to 4x10G SFP+ Passive DAC Breakout Cable
- 40G QSFP+ to 4x10G SFP+ Breakout AOC Cable
How to Realize 4x 25GbE Mode on QSFP28 100G Port
To achieve 100G transmission, four SFP28 can fully utilize the electrical lanes of the QSFP28.
- QSFP28 100G transceiver with MTP/MPO connector; SFP28 25G transceivers with LC connector; MTP/MPO-LC harness cable
- 100G QSFP28 to 4x 25G SFP28 Passive DAC Breakout Cable
- 100G QSFP28 to 4x 25G SFP28 Breakout AOC Cable
How to Restore QSFP28 100G Ports to Default Configuration
The following commands allow you to return the QSFP28 100G port to its default mode.
Configure the port to default mode
- (config)# interface Ethernet1/1-4
- (config-if-Et1/1)# no speed
Restore factory settings
- Switch// delete Startup-config
With the necessary hardware, the switch's QSFP28 100G port can operate in 40GbE, 4x 25GbE, and 4x 10GbE modes in addition to 100G mode. Moreover, it is equally important to understand how to return the switch port to its default mode.
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