[c-nsp] monitoring switch stacks

[Kevin Graham]

> just wondered what folk did out there to monitor switch stacks
> (eg stackwise+ switch stacks like 3750e, 2975gs etc (not the older
> gigastack ones....) ) - using the basic methods such as ICMP will
> only show the presence of connectivity to the stack but not the
> actual health of the stack - eg one member is missing.

Perhaps the easiest for this is walking:

   CISCO-STACKWISE-MIB::cswStackPortOperStatus

...to handle non-stackables or non-stacked stackables, we ignore
on a NOSUCHOBJECT or where row count is <= 2. After those
conditions are satisfied, its reasonable to alert on >= 1 ports
in a state other than up(1).

Stack ports from missing members will still be there (and
obviously in a non-up operStatus), so you catch that state as
well as a partially-cabled stack.

For example, this is a 2 switch stack with a missing member:

CISCO-STACKWISE-MIB::cswStackPortOperStatus.5180 = INTEGER: down(2)
CISCO-STACKWISE-MIB::cswStackPortOperStatus.5181 = INTEGER: down(2)
CISCO-STACKWISE-MIB::cswStackPortOperStatus.5183 = INTEGER: down(2)
CISCO-STACKWISE-MIB::cswStackPortOperStatus.5184 = INTEGER: down(2)

...and this is a 4 switch stack with a broken cable:

CISCO-STACKWISE-MIB::cswStackPortOperStatus.5366 = INTEGER: down(2)
CISCO-STACKWISE-MIB::cswStackPortOperStatus.5367 = INTEGER: up(1)
CISCO-STACKWISE-MIB::cswStackPortOperStatus.5369 = INTEGER: up(1)
CISCO-STACKWISE-MIB::cswStackPortOperStatus.5370 = INTEGER: down(2)
CISCO-STACKWISE-MIB::cswStackPortOperStatus.5372 = INTEGER: up(1)
CISCO-STACKWISE-MIB::cswStackPortOperStatus.5373 = INTEGER: up(1)
CISCO-STACKWISE-MIB::cswStackPortOperStatus.5375 = INTEGER: up(1)
CISCO-STACKWISE-MIB::cswStackPortOperStatus.5376 = INTEGER: up(1)

We had _really_ hoped to also catch 'flapping' stack ports by
watching ifLastChange (since healthy stack ports never change
state), but CSCsr85997 killed that idea.

I would be elated to see CISCO-SWITCH-HARDWARE-CAPACITY-MIB or
its equivalent for these switches (given their limited and 
variably sized resources), but it seems unlikely that will
ever happen...