Re: NetFlow in core routers

From: Christian Hammers (
Date: Thu Aug 09 2001 - 18:22:44 PDT

  • Next message: Hendrik Visage: "Re: NetFlow in core routers"

    On Thu, Aug 09, 2001 at 02:18:36PM -0700, Ajay Shah wrote:
    > Cisco recommends NOT to use NetFlow in the Core. I was wondering about the
    > actual performance / resource impact of doing this.
    I guess the main problem would be to ensure that every packet really passes
    exactly one netflow router and not more.

    In a big network with redundant connections between the routers and more than
    one upstream provider it could easily be that a packet comes in an edge router,
    traverses one core router, goes to the next core router and reaches it's target.
    Deciding which packts to filter on which interface on the core router may
    then be very error prone. On the other side accounting each edge interface on
    each edge router of your net is easy to verify.

    hope that helps,


    Christian Hammers    WESTEND GmbH - Aachen und Dueren     Tel 0241/701333-0     Internet & Security for Professionals    Fax 0241/911879
               WESTEND ist CISCO Systems Partner - Premium Certified
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