Understanding SNMP Support for Routing Instances
Junos OS enables SNMP managers for all routing instances to request and manage SNMP data related to the corresponding routing instances and logical system networks.
In Junos OS:
Clients from routing instances other than the default can access MIB objects and perform SNMP operations only on the logical system networks to which they belong.
Clients from the default routing instance can access information related to all routing instances and logical system networks.
Before Junos OS Release 8.4, only the SNMP manager in the default routing instance (inet.0) had access to the MIB objects
With the increase in virtual private network (VPN) service offerings, this feature is useful particularly for service providers who need to obtain SNMP data for specific routing instances (see Figure 1). Service providers can use this information for their own management needs or export the data for use by their customers.
If no routing instance is specified in the request, the SNMP agent operates as before:
For nonrouting table objects, all instances are exposed.
For routing table objects, only those associated with the default routing instance are exposed.
The actual protocol data units (PDUs) are still exchanged over the default (inet.0) routing instance, but the data contents returned are dictated by the routing instance specified in the request PDUs.