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From: kzm@hls.com (Keith McCloghrie)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: What are the rules for Object Instances?
Message-ID: <9106050557.AA25575@nms.netman>
Date: 5 Jun 91 05:57:32 GMT
References: <9106040008.AA24232@xap.xyplex.com>
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Bob,

Your explanation was accurate, but you may have conveyed an impression 
you didn't intend:

>                                                          For an object with
> multiple instances, such as ifSpeed, the instance identifier suits the object
> and is non-zero.  

This is indeed true for ifSpeed.   However, there is nothing which prohibits
the definition of an instance identifier (i.e. a MIB table's INDEX variable)
which can take the value of zero.  

The closest to an example of this in the core MIB (i.e. MIB-II) is the 
IP Routing Table.  Instances of objects in the IP Routing Table take the
associated route's destination as their instance identifier.  For a 
"default route", the instance of each object has the instance identifier 
of 0.0.0.0 (i.e. four OID sub-identifiers each of which has the value 
of zero).

Keith.