How To
Summary
Recommended FEC (Forward Error Correction) setting for networking connections with 25Gb OSA Express 7S, RoCE Express and Network Express Adapters
Objective
When connecting networking switch ports to an IBM Z networking adapter, utilizing a 25Gb link, it is recommended that both sides of the connection are set to the same FEC (Forward Error Correction) setting in order to establish a link. IBM Z 25Gb networking adapters only support the IEEE RS (Reed Solomon) FEC mode, and as such it is recommended that the switch side is also set to "IEEE RS FEC" mode. This applies for any link utilizing any of the following adapters:
1. OSA Express 7S 25Gb
2. RoCE Express 25Gb
3. Network Express 25Gb
2. RoCE Express 25Gb
3. Network Express 25Gb
Failure to set the FEC mode to IEEE RS FEC on the switch side will most likely result in a link not being established, but may also present symptoms such as loss of packets and/or failure to transmit or receive any data even if a link is established.
Steps
Please consult with your switch vendor for specific instructions on how to set the FEC mode for each interface/port on the switch to "IEEE RS FEC".
Additional Information
IBM Z networking adapters that support 25Gb connections:
- OSA Express 7S 25Gb
- RoCE Express 25Gb
- Network Express 25Gb
Document Location
Worldwide
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Document Information
Modified date:
03 October 2025
UID
ibm17245478