[c-nsp] High SNMP CPU with SXH. Is SXI any better?

Karl Gaissmaier karl.gaissmaier at uni-ulm.de
Tue Dec 16 05:15:38 EST 2008

Hi all,

Phil Mayers schrieb:
>> I haven't looked into it, but perhaps you can find a cisco specific
>> mib, maybe cef or mls specific that doesn't have this performance
> CISCO-SWITCH-ENGINE-MIB::cseCef* are the ones. However, they contain 
> basically the entire FIB & adjacency entries. They're faster to walk, 
> but their size can make the whole process slower :o(

If you use the cseCefAdjacencyTable, the number of entries are
similar to the ipNetToMediaTable.

My tests showed, that fetching the ipNetToMediaTable
stresses the route processor at ~90% cpu load.

Fetching the cseCefAdjacencyTable stresses the switch processor
and the route processor together, but now both processors at
~50% cpu load.

>> penalty?  Otherwise, I bet a query via clogin outperforms the snmp
>> table.
> It certainly does. ~10 seconds versus ~2min 30sec on our busiest router.


a column from the MIB-II ipNetToMediaTable

unix$ time snmpbulkwalk -v 2c cat65-box

5595 entries

real	0m11.699s
user	0m0.128s
sys	0m0.020s

a column from the CISCO-SWITCH-ENGINE cseCefAdjacencyTable

unix$ snmpbulkwalk -v 2c cat65-box

6044 entries

real	0m4.055s
user	0m0.152s
sys	0m0.028s

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Best Regards
Karl Gaissmaier
Kommunikations und Informationszentrum kiz
der Universität Ulm
Abteilung Infrastruktur
SG Netzwerk und Telekommunikation
89069 Ulm
Tel.: 49(0)731/50-22499 Fax : 49(0)731/50-1222499

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