When trying to stack two 9500s we encountered the error below, the switch rebooted but to our surprise the only active switch also rebooted and caused an outage in the network.
SESA: Master authentication failure. Err: 36
While Googling I found a NIST document with the acronym SESA and something about secure stacking.
Lo and behold show secure-stackwise-virtual
is available in the commandline.
Apparently, the active switch had been configured with Secure Stackwise, but the new standby had not. The Secure StackWise configuration is not evident in the show running-configuration
so we simply missed that it was configured.
Once we had configured the authentication key and reloaded the standby switch, we were able to connect the standby without issues.