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Re: Referential integrity across reboots

At 03:39 PM 3/3/2003 -0500, Murthy.N.N wrote:
>Hello Jochen, 
>Can you please elaborate, why such a formula does not work for Logical interfaces? 

I agree with Juergen.  Many logical interfaces are created in an
implementation dependent order.  In general, I believe it is too
late to change the semantics of the ifIndex object now.  There
are too many proprietary algorithms for assigning ifIndex values 
in use to start mandating a standard algorithm now.  It's also
illegal to make such a change, according to SMI rules.

There is a better way to solve this problem.  Instead of standardizing
ifIndex assignments, which will be very hard because of all the
different hardware configurations and logical interface initialization
schemes, standardize a read-only "persistent ifIndex" MIB object. If
'true', then the agent will make a best-effort attempt to assign
the same ifIndex value to an interface across a reboot.  This needs to 
be best-effort because the agent can not always recognize an interface 
across reboots, due to HW or SW reconfiguration.

>Thanks and rgds, Murthy 


>Jochen Friedrich wrote: 
>>Hi Murthy, 
>>> Let us consider an equipment having the entities, rack, shelves, slots, 
>>> cards, ports. Let us assume, maximum number of SNMP interfaces (ex; ATM 
>>> interface, ADSL line interface, ADSL channel interface) supported per 
>>> slot is X. Then, we can device a formula to find out ifIndex of an 
>>> Interface uniquely as follows; 
>>> ifIndex=<rack #> <shelf #> <slot #> <interface # within the slot. 0 to 
>>> X> 
>>> With this formula, one get same ifIndex all the time for a particular 
>>> Interface. 
>>That might work for physical interfaces but will definitely fail for 
>>logical ones (like loopback, tunnel, ELAN, trunk interfaces etc). 
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