This read-write INTEGER identifies a specific network interface on the Digi mobile device, using the same interface numbering as the standard ifIndex value, and per the source its value stays constant for a given interface across the device's re-initializations. An administrator or the device's own trap-generation logic uses this object to indicate which interface a related mobile-status notification (like mobileSuboptimal) is describing, since it's grouped together with mobileInfoName and mobileInfoValue as a name/value pair tied to that interface. For example, a value of 2 would indicate the trap information pertains to the device's second network interface, such as its cellular modem link.