[c-nsp] General switching question regarding load balancing host

Jay Nakamura zeusdadog at gmail.com
Fri Sep 17 12:44:13 EDT 2010

In this specific case, it started with HP/Lefthand iSCSI SAN "Adaptive
Load Balancing" but the question was more general.

On Fri, Sep 17, 2010 at 12:17 PM, Nick Hilliard <nick at foobar.org> wrote:
> On 17/09/2010 16:52, Jay Nakamura wrote:
>> Some hosts/OS can do load balancing between NICs.  If a host has two
>> NICs connected to two switches,(the two switches are connected
>> together) and load balancing between them, switch will see the same
>> source MAC from two ports.  How does a switch decide which ports to
>> put in the forwarding table?  Would it switch back and forth every
>> time there is a packet?  Is there any negative effect on the switch
>> when that happens?  Is this platform dependent?
> Are you talking about Network Load Balancing (NLB) here?  This is very hacky
> stuff which depends on switch port flooding and MAC address spoofing to
> operate correctly.  I wouldn't be the world's greatest fan of this approach,
> to be honest.
>> http://blogs.technet.com/b/networking/archive/2008/05/15/preparing-the-network-for-nlb-2008.aspx
> On switches, it's generally not hardware dependent.
> Nick
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