MACSEC comes UP as expected immediately after it is configured. However, traffic fails between the Cisco switch and Juniper Router.
When initiating a ping from Cisco switch to Juniper router, it is clear that ARP is being learnt on Juniper, while Cisco fails to do the same.
It is also clear that ARP responses are being sent out from Juniper router, but the Cisco switch fails to see them.
Verified with firewall filters on the physical interfaces to ensure that the MACSEC has 'must-secure' configured on both sides, along with the same Cipher suite, which shows the MACSEC status is UP as expected.
In this situation, the 'include-sci' is 'yes' by default on the Cisco switch, while it is optional for Juniper.
Add 'include-sci' on the Juniper Router MACSEC configuration as follows:
#set security macsec connectivity-association connectivity-association-name include-sci