This KB is related to MACsec support on the EX4100-48P switch when connected to host devices.

Does the EX4100-48P switch support IEEE 802.1AE (MACsec) on access ports connected to PCs or end-user devices?

A valid MACsec feature license is required to configure and enable MACsec on EX Series and QFX Series switches. The only exceptions are the QFX10000-6C-DWDM and QFX10000-30C-M line cards, which do not require a separate MACsec license.

If the MACsec license is not installed on the device, MACsec configuration cannot be activated, and MACsec functionality will not be available on the switch interfaces.

Therefore, before configuring IEEE 802.1AE (MACsec) on EX4100-48P access ports connected to host devices, ensure that the appropriate MACsec feature license is installed on the switch.

https://www.juniper.net/documentation/us/en/software/junos/security-services/topics/topic-map/understanding-macsec.html