Oliver Boehmer (oboehmer) <> wrote on Monday, June 16, 2008 3:58 PM:
> Peter Haag <> wrote on Monday, June 16, 2008 3:02 PM:
>
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>> Hi Cisco gurus,
>> For the next developing steps for my nfdump tools, I would like to
>> implement sampling - a feature, which a lot of users would like to
>> have. Sampling for v5 is announced in the v5 header and therefore
>> easy to recognize. For v9, the tags 34 and 35 (SAMPLING_INTERVAL and
>> SAMPLING_ALGORITHM ) are defined in the specs, but it seams as the
>> IOS does not export sampling information using these tags. Googling
>> lots of CISCO papers does not reveal more information on this issue.
>> So can anybody shed some light on the question how IOS announces
>> sampling in v9? Which platform/IOS combination do work or are
>> required to get sampling information in the netflow records?
>
> I think we only export the v9 fields related to sampling information
> when using Flexible Netflow and enabling "option sampler-table".
> Within the "traditional" Netflow infrastructure, these fields are not
> sent IIRC (many customers use the same sampling interval throughout
> the network, so entering this information statically somewhere works
> for many deployments)..
I think I need to correct myself:
ip flow-export template options sampling
sends the sampling information as part of an option template with
option id=48 (FLOW_SAMPLER_ID)
option id=49 (FLOW_SAMPLER_MODE)
option id=50 (FLOW_SAMPLER_RANDOM_INTERVAL)
Don't have a setup to try this on right now (and haven't touched Netflow
in a while ;-)
oli
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