Can I access a list of all routing instances on a device?
Yes, you can access a list of all the routing instances on a device using the vacmContextName object in the SNMP-VIEW-BASED-ACM MIB. In SNMP, each routing instance becomes a VACM context; this is why the routing instances appear in the vacmContextName object.
You cannot access a default routing instance from a client in another logical router or routing instance. The SNMP agent can only access data of the logical router to which it is connected.
For more information, click Understanding SNMP implementation in Junos OS.