HA on two or more switches

Ben Cahill
  • Ben Cahill

    Ben Cahill - 2001-11-01

    Please advise a newbie link-agger . . . .

    In the "Linux Ethernet Bonding Driver Mini How-To" in the patch, in the "High Availabilty" section, it shows an example for HA for a "no single point of failure" (Example 1).

    It states that the MAC address should be visible on only one port, to avoid confusing the switches.

    Is this confusion caused by the Inter-Switch Link?  Without the ISL, the switches would be independent from one another, and should be able to handle link aggregation (that is, each switch would see only one port with a given MAC address, so each switch would never even be aware of aggregation).

    If the ISL is the source of confusion, is there a way to configure the switches to know better?

    Or, is the source of confusion the "outside world" connected to ports 3 in the example?


    -- Ben --

    • Graham Wood

      Graham Wood - 2001-12-20

      The ISL indeed causes the confusion - since without it you would just have 2 separate networks. But then you would end up with a bridged network instead of bonding, and that is covered somewhere else....

      Configuring the switches to support it would be very ugly - since they would have to communicate to each other that they both had access to that MAC, or even that IP.

      I don't know of any switches that would support it, although it would be nice. *GRIN*

    • Adam

      Adam - 2002-09-16

      In response to the last message, such a switch does exist. The Nortel Passport 8600 is able to be linked to another 8600 via a high speed IST (inter switch trunk) and appear as one logical switch to multi-homed servers or switches for that matter.

    • Anonymous - 2002-11-20

      Following on from the post by Adam, as well as the Nortel Passport8600, the Nortel Business Policy Switch, and BayStack4xx switches can also provide etherchannel bonding over two separate switches. I mention this as these switches are much cheaper than the Passport8600 switches.
      FWIW, there is some generic info at:


      The BayStack switches support Distributed MultiLink Trunking, which is similar to Split Multi Link Trunking




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