When two VSP 8606CQ modules are connected back to back, the MACsec connection works only if the software version on both ends are the same. The modules must be running a supported release starting with Release 6.1.x. If, for example, one end is running 6.1.x and the other end is running a different release, MACsec will not work and traffic will drop.
With this new implementation of MACsec on the 100 Gb 8606CQ module, the MACsec statistics increment the Unchecked Packets counter on the receiving link and not the Accepted or Validated counter. This counter issue happens only when encryption is disabled on both the transmitting and receiving links.