Michael Patterson : Advanced NetFlow Traffic Analysis
Michael Patterson
Founder and Product manager for Plixer's Scrutinizer NetFlow and sFlow Analyzer as well as Flow Analytics.

March 2013

You are browsing the archive for March 2013.

Building a NetFlow Cache: Exporting IPFIX

March 12, 2013

Most engineers implementing NetFlow or IPFIX know how to get started.  Where they sometimes stumble is in the area of a properly structured export with well thought out relationships between the templates. Today I want to provide an good example.

This  post on building a NetFlow Cache and exporting IPFIX is pretty deep. For this reason, my prior post on Exporting NetFlow or IPFIX   really should be reviewed first.  A flow cache entry in a router or switch is built using the first packet between two hosts and the cache table is maintained for all active connections (i.e. flows).   When a packet comes into the device, its tuple is compared to existing entries in the cache table.  A match of the key fields triggers a flow entry update where packet, byte counts and perhaps other fields are incremented and updated. Packets that don’t match a flow entry are compared to policy (e.g. firewall or ACL rules) and are ultimately dropped or used to create new cache entries.  Flow entries are exported to a flow collector periodically based on timers (I.e. Active Timeout) or flow behaviors.

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