On 18/11/2007, oleg@gomelpromstroy.by wrote:
> -- Why are updated only every 30 seconds?

When the agent receives a request for any information from
the ifTable, it will read in the data for *all* interfaces. This
process is relatively expensive, so it is cached for later use.
This helps when walking the whole table.

> -- In version smnpd 5.1.2, the data are updated through 1 second

The 5.1.x code didn't have much support for data caching, so most
MIB modules (including the ifTable) would retrieve data afresh for
every single request. This gives more up-to-date information, at
the cost of increased processing overheads.

Later release lines improved the caching support, so the newer
ifTable implementation makes use of this facility.

> -- In man snmpd.conf found mention about versionClearCache,
> thinking that might help

Probably not.
But have a look at the NET-SNMP-AGENT-MIB::nsCacheTable.
That should allow you to tweak the expiry time of the ifTable cache,
or turn it off completely (by setting it to 0).


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