>>> [...if_index...]
>> What you're supposed to have in addition to the index is a way to
>> use it to query for all the other state associated with the
>> interface.  Then the index can become the canonical way for software
>> to refer to an interface, leaving the pretty ascii name for humans
>> to use.
> well...if there was a kernel interface that could make use of said
> numbers...that'd be cool.  as it is, they're not much good to me.  i
> used it in the kernel once, though.  there it was good.

This perhaps has something to do with your attempts to manipulate ARP
entries failing; looking at the code for the program that deals with
them, I find that when creating ARP entries, I use if_index values to
name interfaces there.

I don't know offhand of any other interface that uses index values to
name interfaces.  My code never goes the other way; it looks up the
index values for the interfaces it cares about, but never has occasion
to map from index values to the interface in any other sense.

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