Refer to the exhibit:According to the HPE Aruba Networking VSX best practices, what would need...

In the exhibit, the CX8325 switch ports 1/1/47 and 1/1/48 are connected in a VSX setup. According to Aruba VSX best practices, ports on the CX8325 switch that serve as ISL or VSX interconnects should use SFP28 optics for 25Gbps links. If SFP56 optics are used, it would be incorrect because CX8325 ports are designed to support SFP28 modules for these speeds.

CX6300 ports use SFP56 or QSFP28 depending on model and link speed.

CX8300 series ports designed for QSFP28 for higher speeds.

Hence, the best practice is to use SFP28 on CX8325 for the interconnect links.