Re: OIDS

On 25/07/06, Jonathan Shan <[email protected]> wrote:
> Why do I need to append a "0" to the end of some OIDs?
> Sometimes the "0" doesn't work and a 1 is needed.

Every management value is an "instance" of the abstract MIB object.
Some objects only ever have one instance - these are known as scalar objects.
Other objects can have several instances - structured in the form of a table.

With table-based objects, you clearly need some way to distinguish
between the various instances of that object.  This uses the "instance
subidentifier" which is appended to the OID of the object itself.
Sometimes this is a simple integer, such as the ifTable.  Sometimes
it's a string, or an IP address, or some other more complicated form
of instance indexing.  Try "snmpwalk .... tcpConnTable" - that uses
two IP addresses and two integers to index the table.


With scalar objects, there's only one possible value, so an instance
subidentifier isn't strictly necessary.  But to keep things in line
with table OIDs (where you have to add an index to the base OID), the
same approach is used for scalars as well.  You always have to add the
"scalar instance subidentifer" to the MIB OID, which is this 0.


OK?

Dave

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