Re: ng_fec and cisco 2931

From: Lars Erik Gullerud (lerik_at_nolink.net)
Date: 03/02/05

  • Next message: Michael G. Jung: "ng_fec and cisco 2931" 
    Date: Wed, 2 Mar 2005 18:58:02 +0100 (CET)
To: Lister <lister@primetime.com>

    On Sun, 27 Feb 2005, Lister wrote:

    >
    > I have setup ng_fec on a machine with a quad ethernet NIC :
    [snip]
    > I have all 4 ports connected to the catalyst. From what I have read on
    > fast etherchannel in the cisco docs, it is supposed to detect the
    > etherchannel,
    > e.g. no commands at the switch. Lights blink on and off, change color
    > (orange -> green) and it seems to work ... but only on one interface in the
    > bundle. No faster than 80Mb. I have a 1000Mb intel card in the 2nd
    > test machine that does run much faster than 100.
    > So, is there something I have done wrong, or what? What should I expect
    > to get from 4 x 100 Mb ports?

    Not really related to FreeBSD's ng_fec at all I think, this is a common
    FEC issue.

    If you are testing this between two hosts as you indicate above, then you
    are getting exactly the speed you should be getting. The low-end Cisco
    switches offers two varieties of "load-balancing" over the FEC members,
    source or destination-based hash (both operate on MAC-address level). So
    if all your test traffic goes between a set of two mac-addresses, traffic
    in either direction will only flow over one member of the FEC.

    The higher-end devices like the 6500 series can also look at layer 3 and
    layer 4 flow-information to distribute the load, but basically a FEC is
    mostly useful in scenarios where you have a large number of hosts
    communicating.

    /leg

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