The 3810M require stacking link modules with stacking cables. The macsec module are simple sfp+ connections with macsec capability.
Stacking Modules
System (std 0 // max=1) User Selection (min 0 / max=1) per Chassis Aruba 3810M 4-port Stacking Module
• min=1 \ max=4 Stacking cables Configuration Rules:
JL084A See Configuration NOTE: 1
J9578A J9665A J9579A
NOTE 1
Uplink Modules
One of the following Stacking Cables must be selected:
Aruba 3800/3810M 0.5m Stacking Cable Aruba 3800/3810M 1m Stacking Cable Aruba 3800/3810M 3m Stacking Cable