Re: To get a row/column objects

A minor amendment to what Mike said:

2008/7/30 Mike Ayers <[email protected]>:

>        The MIB says:

   <snip/>

> [SNIP]
> ifIndex OBJECT-TYPE
>    SYNTAX      InterfaceIndex
>    MAX-ACCESS  read-only
>    STATUS      current
>    DESCRIPTION

>    ::= { ifEntry 1 }
> [/SNIP]
>
>        You will never see one of these objects.

In a well-designed table, this would be true, for exactly the reasons
Mike outlines:

>  Why?  Because it's an index (see the INDEX clause of ifEntry),
> and in SNMP indices are never returned as objects, since they
> are already included as part of the OID.

Unfortunately, the ifTable is a hold-over from the very beginning of
SNMP, when men were men, women were women, and MIB table
design was not particularly well understood.

So this particular index column *does* actually appear in the output
of the agent.  This information is completely redundant, and there's
no point in returning it like this, but the MAX-ACCESS clause says
"read-only" so the agent will return it.

A better designed table would have a MAX-ACCESS clause of
"not-accessible", and would indeed omit the index column
altogether.


So:
>        To sum it all up the first returnable object is ifTable.ifEntry.ifDescr, or ifTable.1.2 .
>  If you get next on ifTable, the correct response is ifTable.1.2.(first index).
>  If you get next on ifIndex.1, or ifTable.1.1, the correct response is ifTable.1.2.(first index).

*ought* to be true, but isn't.
The first returnable object is actually ifTable.ifEntry.ifIndex  (ifTable.1.1)
and these GETNEXTs would actually return ifTable.1.1.(first index)

Dave

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