There are two kinds of MIB objects:
- Scalar value - a single value, such as the interface number shown above. For example, the ifNumber MIB object of a router is a single number that represents the total number of its interfaces (ports).
- Table entry - provides the same piece of information for different items, such as the traffic for each of a router's ports, information about each of the TCP connections in a device, or the amount of paper in each of a printer's trays.
Intermapper reads and displays both scalar values and table entries in its SNMP probes.
A scalar value must have a ".0" suffix in its OID. For example, the OID for ifNumber in MIB-II is often written as
In a probe, it should be represented as
(This ".0" is technically part of the OID - it's convenient not to write it, though.)
A table object is generally suffixed with the index of its row. ( This isn't always true: see About Table Indexes below.) For example, the Cisco Environment Monitoring MIB defines two objects for the input air temperature and input voltage as the first rows in each of these tables:
If you add a suffix ".1" to each of these, you'll get the value of the first row; add ".2" to as a suffix, you'll get the second row, etc.
About Table Indexes
As noted above, some tables don't have a separate index column. These rows are named (their OIDs are specified by) data in the row. For example, the OID for tcpConnState row, the status of a particular TCP connection is
Its index is the source and destination IP address and port (all four values) which are appended to the tcpConnState OID. Thus, the full OID for the state of a TCP connection from 18.104.22.168 port 543 to 22.214.171.124 port 8765 would be: