We are looking into 547FLR-QSFP (40 GbE) or MCX4121A-ACFT (10/25 GbE) for our HPE Apollo 4510 servers. As we do not have top of the rack switches everywhere the max distance to a switch in the same row is ~7m. The second switch will be in a different row and it will be definitly > 7m.
The 547FLR-QSFP does only support 5m DAC cables and MPO Tranceivers.
- HPE FlexNetwork X240 40G QSFP+ QSFP+ 5m Direct Attach Copper Cable JG328
- HPE X140 40G QSFP+ MPO SR4 Transceiver JG325B
So 5m DAC is too short and MPO is not used here in datacenter. My network collegues prefere BiDi cables for 40G as they are cheaper and use less fibres than the MPO, but BiDi is not supported with the 547 adapter, there is an advisory about a problem with BiDi tranceivers and these adapters. So we can not use the 547 adapter. AOC cables are also not an option.
The MCX4121A-ACFT also supports only 5m DAC cables with Cisco switches, at least according to COMPUTE TRANSCEIVER AND CABLE HARDWARE MATRIX but at least a more common SFP28 LC typ.
- 844480-B21 HPE 25Gb SFP28 to SFP28 5m DAC
- 845398-B21 HPE 25Gb SFP28 SR 100m Transceiver (https://h20195.www2.hpe.com/v2/GetDocument.aspx?docname=c04939512)
On switch side we use a Cisco SFP-25G-SR-S tranceiver.
https://www.cisco.com/c/en/us/products/collateral/interfaces-modules/transceiver-modules/datasheet-c78-736950.html
Cisco SFP-25G-SR-S
The Cisco 25GBASE-SR Module supports a link length of 70/100m on OM3/4 MMF.
This module requires RS-FEC on the host ports.
I'm not sure about the RS-FEC as it is not mentioned for the HPE adapter or tranceiver.
Am I missing anything, or ist this tranceiver the only option to connect the 25G adapter MCX4121A-ACFT to switch with a distance > 7m and DAC or fibre cable?
