# Querying SNMP Interface Tables, considerations



## commx (Jan 30, 2013)

Hi there,
this is probably not a question related directly to FreeBSD (so feel free to move this Thread if its not in the appropriate place).

At this time I'm writing some kind of a Network Monitoring Service that keeps an eye on SNMP-based Switches. It should query the Switches, lets say every five minutes, to collect their counters. Works almost like every other solution on the marked to create graphs of the interface usage. However, I have no idea how much impact SNMP has on the devices itself. If you have rather old hardware and you do a snmpwalk through the whole Interface Table, it may require more computing power than just querying one single Interface.

There is just one problem: I don't know if it makes more sense to fetch the whole Interface Table at once, or to fetch the counters (in+out) for each individual device. This can be, depending on how much interfaces are configured to be fetched, up to 48 interfaces * 2 = 96 SNMP queries vs. 1 SNMP query when doing a single snmpwalk through the ifTable.

Which makes more sense? And how much impace does it actually have (guess?)

Thank you


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## SirDice (Jan 30, 2013)

We do hundreds of queries to each device. Besides the counters we also get the configs, ACLs, CAM tables and what not. Impact is minimal. Unless there's a bug in the SNMP implementation of that device (we have had that happen too).


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