USG9520 license activation issue , USG9520 has two boards , main board and slave board , each board has ESN respectively , how to active a license to ensure the additional feature running normally.
two ways :
1. apply license with the ESN of backplane , then active the license on USG9520 one time.
2. apply two licenses with the ESN of two boards respectively , then active the two licenses on USG9520 respectively.
both of the two approaches can ensure additional feature running normally even if switch between main and slave take place.