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RE: Switch load balancing posted 02/03/2007
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When the intermediate switch in the path (Sw2 & Sw3) has only one
physical connection to each ends (Sw1 & Sw4) as in this case, there is no
different than a link directly between two end points because the
intermediate switch has only one path to the destination.  It's not like
SW1 sends a frame to Sw2, then Sw2 has a choice wheter to send to sw 4
via SW3, or any other link.  There is only one link, no choice for SW2
but to forward it to an only path to Sw4.  In brief, setting load
balancing on Sw1 & Sw4 is sufficient in this case. When the intermediate
switch has multiple paths to the destination, it's best to mix up the
algorithm so that the load balacing scheme is different.  If all the
devices using the same algorithm, it will lead to CEF polarization.
Regards, Tom

  ----- Original Message -----
  From: graham@xxxxxxxxxxxxxxxxxx
  To: "'Joe Yohannan'" , ccielab@xxxxxxxxxxxxxx
  Subject: RE: Switch load balancing
  Date: Sat, 3 Feb 2007 17:58:07 -0000


  Agreed this was my initial thought

  But SW1 and SW4 arent directly attached and each are connected to SW2
  and
  SW3 via a single link, can a port channel be done over multiple hops?

  -----Original Message-----
  From: nobody@xxxxxxxxxxxxxx [mailto:nobody@xxxxxxxxxxxxxx] On Behalf
  Of Joe
  Yohannan
  Sent: 03 February 2007 17:15
  To: graham@xxxxxxxxxxxxxxxxxx; ccielab@xxxxxxxxxxxxxx
  Subject: RE: Switch load balancing

  The 3560 offers a "src-dst-ip" option under the port-channel
  load-balance
  command. It sounds to me that that is what the question is looking
  for.

  - Joe


  > From:
  > Reply-To:
  > To:
  > Subject: Switch load balancing
  > Date: Sat, 3 Feb 2007 17:06:09 -0000
  >
  > Hi group,
  >
  >
  >
  > I'm working on a question which asks to load balance between two
  switch
  > endpoints 1 and 4
  >
  >
  >
  > The layout is
  >
  >
  >
  > ----------------- SW3------------
  >
  > SW1< >SW4
  >
  > ----------------SW2--------------
  >
  >
  >
  > Question in its self is not hard but the sting is, where you have a
  choice
  > you must prefer source/destination ip Balancing?
  >
  >
  >
  > Now the load balance method that came to mind was a Layer 3
  etherchannel and
  > port-channel load balancing, but I can't see how that would fit in
  this
  > scenario? Should I ignore the bit at the end which stipulates where
  you have
  > a choice?
  >
  >
  >
  >
  >
  > Thanks
  >
  >
  >
  > Graham
  >
  >
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