[Isis-wg] ISIS MIB question

[He, James]

>>Let's start with the easy one.

>>You might have multiple adjacencies on a LAN interface,
>>such as Ethernet.  In this case, you will need to 
>>distinguish adjacencies which share the same circuit
>>attributes.  The AdjIndex serves to mark such different
>>adjacencies: clearly no circuit index can do that job.  

>I understand that you can have multiple adjacencies on
>a LAN interface. But my question is why do you need to
>'assign' an AdjIndex to distinguish adjacencies when 
>there seems to be enough other information to uniquely
>identify an adjacency without it?  Specifically, why can't
>you use isisISAdjNeighSNPAAddress in combination with the
>circuit attributes to distinguish an adjacency?  Are SNPA
>addresses not unique?

>         isisISAdjIndex OBJECT-TYPE
>             SYNTAX Integer32
>             MAX-ACCESS not-accessible
>             STATUS current
>             DESCRIPTION
>                 "A unique value identifying the IS adjacency from all
>                 other such adjacencies on this circuit. This value is
>                 assigned by the system when the adjacency is created
>                 automatically."
>         ::= { isisISAdjEntry 3 }

There might be two adjacencies between two systems. Hence 
isisISAdjNeighSNPAAddress is not enough the identify a particular
adjacency. 




>Is there a default value for this object when a
>subinterface index might not apply? On a LAN
>circuit, for instance.

It might be -1 or 0.



James