[c-nsp] AS53xx and SNMP OID modems-DS0s in use - bug

[Robert Blayzor]

We have several AS53xx access servers deployed.  For well over a year
we've been running IOS 12.3(x) without a single problem, the last
version being 12.3(13a) which seems to be fine.

We've recently upgraded a few to 12.3(17a) and now 12.3(18) (mainline).
 Since then we've noticed that the SNMP OID's used to gather the number
of DS0's and/or modems does not work correctly.

The OID in question: 1.3.6.1.4.1.9.10.19.1.1.4.0

On our AS5300's still running 12.3(13a) this works as normal and the
value returned in SNMP is accurate with the number of active calls on
the router.  On one of the access servers running 12.3(13a) with a fair
amount of uptime I get the proper response:

snmpget -c public x.x.x.x 1.3.6.1.4.1.9.10.19.1.1.4.0
SNMPv2-SMI::enterprises.9.10.19.1.1.4.0 = Gauge32: 116


Now on one with about a month of uptime running 12.3(17a):

snmpget -c public x.x.x.x 1.3.6.1.4.1.9.10.19.1.1.4.0
SNMPv2-SMI::enterprises.9.10.19.1.1.4.0 = Gauge32: 5249


So on the new version it seems that this number slowly creeps up,
incrementing over time to where the number grows in the thousands.  It's
almost as though the value misses a decrement internally when a call
disconnects.  When this happens all of our MRTG collectors start storing
numbers that are out of bounds.

I've done some searching but can't seem to find if it's a bug.  I'm not
exactly sure which version between 12.3(13a) and 12.3(17a) actually
broke it, but I do know that it's broken in 12.3(18) as well.

Anyone else run into this?

-- 
Robert Blayzor, BOFH
INOC, LLC
rblayzor\@(inoc.net|gmail.com)
PGP: 0x66F90BFC @ http://pgp.mit.edu
Key fingerprint = 6296 F715 038B 44C1 2720  292A 8580 500E 66F9 0BFC

That's a great computer you have there; have you considered how it would
work as a BSD machine?