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Minimal AM335x ALE Configuration

Richard Ames
Prodigy 100 points

I would like to configure the AM335x ALE so that it will forward appropriately between all ports, including the host port, like an externally connected Ethernet switch.  Intuitively, I would think that resetting and clearing the ALE and setting all ports to learning mode would accomplish this, but this isn't the behavior I am seeing.  I have been reviewing the AM335x Technical Reference Manual, especially the ALE section.  I see dual mac mode being described in more detail, but I'm not sure about the mode I describe.  Are there additional steps I need to take?

Thanks for your help,

Richard

  • 0
    Mastermind 8040 points

    Learning mode will learn MAC addresses by creating ALE entries, but packets are dropped rather than forwarded. As the name suggests, to forward packets a port needs to be in forwarding state.

    I posted a tested minimal switch setup procedure on the dm814x forum.  The am335x should be similar (though beware, for some inexplicable reason various register blocks have been reordered and some control bits have been moved from one register to another).

    Keep in mind however that this will not result in a well-behaved standards-compliant switch.  Without proper execution of the Spanning Tree Protocol and such, packet loops could occur for example.

    Matthijs

  • 0 in reply to Matthijs van Duin
    Prodigy 100 points

    Hi Matthijs,

    Thank you for the helpful information.  If I think of the ALE as being designed with the goal of implementing the spanning tree protocol things make more sense.  I'll try out your suggested procedure and follow up.

    - Richard