[c-nsp] L2 SNMP performance on Cat65/76?

[Simon Leinen]

Chris Griffin writes:
> Lately we have been having performance issues with SNMP queries to 
> Sup720 based systems when gathering Layer 2 information (ifOperStatus 
> and several layer 2 traffic counters).  SNMP for these elements will be 
> dropped for long periods of time (5-15 minutes).  This normally happens 
> during network reconvergence events, but sometimes just happens.  During 
> these intervals queries for layer 3 information (BGP etc) occur just 
> fine.  I assume this is because in native IOS, the snmp query has to be 
> relayed to the sup from the msfc?

I think you are correct.  We sometimes see problems reading ifInOctets
& friends via SNMP when a router is exporting a lot of (Net)flows.
MSFC (RP) load is low, but Sup (SP) load is high, and this apparently
starves particular SNMP requests - "Layer 2 information" sounds like a
good description.

> Any tips on making it a bit more responsive even during convergence?
> IOS is 12.2.18SXF7.

Hm, no idea.  I assume the Sup (SP) is busy programming the hardware
forwarding table (MLS TCAM).  You can try "remote command switch show
proc cpu [hist]" to find out more.  But anyway, I don't have any hints
on tuning the Sup - can things like scheduler quantum even be
configured on the Sup?

One promising approach would be to reduce the size of your routing
table by running partial routing (with default).  Besides reducing
convergence issues and hardware FIB maintenance overhead, it saves a
lot of memory and saves you from upgrading to Sup720-XL... oh,
probably you got those already.

Best regards,
-- 
Simon.