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a. Minimum fiber bandwidths in MHz/km for multimode fiber optic links are included in parentheses, where applicable. 

b. With OSA-Express5S, the only link rate supported is 1000 Mbps. 

## 25GbE RoCE Express2.1 

25GbE RoCE Express2.1 (FC 0450) is installed in the PCIe+ I/O drawer and is supported only on IBM z15 servers. The 25GbE RoCE Express2.1 is a native PCIe feature. It does not use a CHPID and is defined by using the IOCP FUNCTION  statement or in the hardware configuration definition (HCD). 

Switch configuration for RoCE Express2.1:  If the IBM 25GbE RoCE Express2.1 features are connected to 25GbE switches, the switches must meet the following requirements: 

GLYPH<SM590000> Global Pause function enabled 

GLYPH<SM590000> Priority flow control (PFC) disabled 

GLYPH<SM590000> No firewalls, no routing, and no IEDN 

The 25GbE RoCE Express2.1 feature does not support auto-negotiation to any other speed and runs in full duplex mode only. 

10GbE and 25GbE RoCE features should not be mixed in a z/OS SMC-R Link Group. Mixing same speed RoCE features in the same z/OS SMC-R link group is allowed. 

The maximum supported unrepeated distance, point-to-point, is 100 meters (328 feet). A client-supplied cable is required. Two types of cables can be used for connecting the port to the selected 25GbE switch or to the 25GbE RoCE Express2.1 feature on the attached server: 

GLYPH<SM590000> OM3 50-micron multimode fiber optic cable that is rated at 2000 MHz-km that ends with an LC Duplex connector, which supports 70 meters (229 feet) 

GLYPH<SM590000> OM4 50-micron multimode fiber optic cable that is rated at 4700 MHz-km that ends with an LC Duplex connector, which supports 100 meters (328 feet) 

On IBM z15 servers, both ports are supported by z/OS and can be shared by up to 126 partitions (LPARs) per PCHID. The 25GbE RoCE Express2.1 feature uses SR optics and supports the use of a multimode fiber optic cable that ends with an LC Duplex connector. Both point-to-point connections and switched connections with an enterprise-class 25GbE switch are supported. 

