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AM3352: Dual Ethernet support with unique MAC

Alberto Soattin
Genius 16905 points
Part Number: AM3352

Hi Support,

is it possible to use AM3352 as single MAC node, but featuring Dual ETH with internal switch (even if PRU is missing in this part)?

Thanks and regards,

Alberto

  • 0
    TI__Guru**** 393215 points
    Hi Alberto,

    I don't quite understand your question. The AM335x CPSW can be configured in Dual EMAC mode, but each EMAC has its own unique MAC address. Is this what you ask?
  • 0 in reply to Biser Gatchev-XID
    TI__Genius 16905 points
    Hi Biser,

    question is if the two EMACs can have the same IP address, because customer need to see the same address for the node.
    Thanks,
    Alberto
  • 0 in reply to Alberto Soattin
    TI__Guru**** 393215 points
    I'm not sure this is possible. I will ask the Ethernet experts to comment.
  • 0 in reply to Alberto Soattin
    TI__Guru 65405 points

    Hi Alberto,

    It is not correct to use two network interfaces with same IP address. This will cause embarrassing of ARP work.
    There is a possible solution if you add both interfaces in a bridge and set an IP address to the bridge. You can find a description about how to do that at:



    BR
    Tsvetolin Shulev

  • 0 in reply to Cvetolin Shulev-XID
    TI__Genius 16905 points
    Hi Tsvetolin,

    let me better specify what customer need: they have a "real switch", so each port need to be able to address data to other ports. I can summarize the two possible use cases as following:

    1) Pure Switch: 1 MAC and 1 IP Address
    2) Dual MAC: 2 MAC and 2 IP Addresses

    Is this feasible with AM3352 ETH?
    Thanks,
    Alberto
  • 0 in reply to Alberto Soattin
    TI__Mastermind 40130 points

    Hi Alberto,

    The listing of options that you have is correct, Switch mode means 1 IP address even though there are 2 physical external ports and PHYs. In dual mac mode the ALE configure as 2 ports which can supports 2 MAC and 2 IP addresses. I need to add that in switch mode the IP address is for a single subnet. Whereas the dual mac has two IP addresses and both ports must be connected to different subnets, (e.g. eth0 192.168.0.x and eth1 192.168.1.x). Another point I need to add is that placing both ports on the same subnet will most likely take down both ports. Here is a presentation that describes why you can't put both ports on the same subnet.

    training.ti.com/.../ETH_System_SW_on_AMClass_Devices.pdf

    If the ports are desired to be redundant other protocols are used.

    The am335x-evmsk is an example of how this two option capability is implemented. By adding the dual-mac flag in the DTS file for the board is how to configure the CPSW driver for dual mac mode. Remove the flag and the CPSW driver will initialize as a switch. No hardware changes are required.

    Let me know if there are additional questions. Also please attach a topology of the customer's intended use of the ports.

  • 0 in reply to Schuyler Patton
    TI__Genius 16905 points

    1783_001.pdfHy Schuyler,

    thanks for the very useful material. Customer studied it and find it solid and well explaining all possible configurations.

    One more question is related to slide #55. What is the reason why a wrong ETH port is replying to the ARP message?

    Please find in attachment the slide I'm referring to.

    Thanks and regards,

    Alberto

  • 0 in reply to Alberto Soattin
    TI__Mastermind 40130 points
    The best I can give at the moment is this is kernel routing issue. The host owns the ip addresses the interfaces do not. In the example the wrong ethernet was used by the kernel ARP response since it matched subnet for the default route table which in this case is eth0 even eth1 is the intended port.

    It might be possible to add ethernet interfaces on the same subnet but routing tables will need to be created. Does the customer require 2 interfaces on the same subnet? If so there are protcols that could be used to provide link redundancy if that is the goal.