Instance Specification -- Tables And Lists

For example, in the "{ interfaces }" group, the first data type is a scalar, thus:

ifNumber ::= { interfaces 1 }

This is the number of interfaces a device has, regardless of their status. The MIB then goes on to define:

ifTable ::= SEQUENCE OF ifEntry

and

ifEntry ::= SEQUENCE {
    ifIndex ::= INTEGER,
    ...
    ifOperStatus::= INTEGER,
    ...etc }

As an example, to retrieve information about (for example) the operational status of interface number 3, where multiple interfaces are in use, we could use:

get interfaces.ifTable.ifEntry.ifOperStatus.3

This would return one of three integer values: 1 for up, 2 for down and 3 for testing, see MIB definition.