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

[Nick Hilliard]

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