Cisco HyperFlex hardware models include redundant ethernet connectivity using SFP+. Cisco recommends at least 10GbE to avoid the network becoming a performance bottleneck.
Cisco also supports 40GbE Fabrics as of HX 2.0.
Ciso HyperFlex M4 models have 10GbE onboard; Cisco HyperFlex M5 models have 40GbE onboard.
As of HX 3.5 Cisco HyperFlex Edge bundle supports both 1GbE and 10GbE.