This article describes two methods of finding Engine ID via SNMP on SRX and other Junos based platforms
There are two methods to query SNMPV3 engine ID: (i) Query the engine ID via SNMP root@R1> show snmp mib get snmpEngineID.0 snmpEngineID.0 = 80 00 0a 4c 04 64 74 5f 4c 67 65 43 45 5f 6d 78 38 30 (ii) check in the cli or via netconf RPC: root@R1> show snmp v3 general | display xml | match engine-id <engine-id>80 00 0a 4c 04 64 74 5f 4c 67 65 43 45 5f 6d 78 38 30