[j-nsp] Rationale behind "set chassis aggregated-devices ethernet device-count"

Phil Mayers p.mayers at imperial.ac.uk
Fri Aug 23 13:14:39 EDT 2013

On 23/08/13 18:04, Doug McIntyre wrote:

> But imagine the case, where you start with needing 4 LAGs, so that is
> what you set. Then you add in 10 SFPs for various things, and then you
> add in 4 more LAGs, then you remove 4 SFPs for some other project.
> What do your SNMP indexes look like now? And hopefully your
> /var/db/dcd.snmp_ix file doesn't get corrupt and the indexes have
> to be recomputed at that point..

Sorry, but I've not understood what point you're trying to make here. 
That adding and removing interfaces will change which ifindex values are 
allocated? Well.... yes, obviously ;o)

(IMNSHO, software that assumes persistent ifindex values is broken and 
should be thrown away)

> Back to the original question, there probably is some resources taken
> up by having the LAGs there. And if you just do max # right away, you do
> have all those new interfaces to gather stats on if your SNMP queries
> just do a bulk walk of all interfaces.

That might be a reasonable explanation, but you could equally well argue 
that putting the interface into the IF-MIB when it's not defined under 
the "interfaces" stanza (as JunOS does) is dumb.

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