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Original question:

CC3220MOD: DHCP server

CC3220MOD: ARP table expiry timings

Vincent Vuarnoz
Expert 2545 points

Part Number: CC3220MOD

Hey community ! 

I guest the most suitable person to answer would be . As he has followed the related thread.

Well, we have not implemented the proposed solution yet. We have simply set the lease time to 17 days. And we are seeing the same issue (in less than 17 days so the lease time cannot possibly be elapsed). 

1. Do you see any other cases where this behavior can happen ?

2. Do you have the exact timing of the automatic flush of the ARP table ?

Thank you !

  • 0
    TI__Mastermind 40965 points

    Hi,

    The ARP entries stored in the ARP table of the CC3220 will expire after 14400 seconds, or 4 hours. At that point, the ARP entry will be marked as stale and the CC3220 will send out another ARP request if needed to that IP address.

    Assuming that you have set your DHCP server's lease time to 17 days, then the CC3220 ARP entry should expire before reuse of the IP address will occur. Thus, I do not know offhand why you may be still seeing the same issues even after adjusting your DHCP server.

    Are you able to perform air sniffer captures to see the full UDP packet interaction flow?

    Regards,

    Michael

  • 0 in reply to Michael Reymond
    Genius 5085 points

    Hi Michael,

    The API's of ARP is not for CC3220 board. I remembered that it was for the CC32XX devices.

  • 0 in reply to Manish_Thakur
    TI__Mastermind 40965 points

    Hi,

    The API for manually sending an ARP request is CC3x35 exclusive. However, the API to flush the entire ARP table and thus indirectly trigger ARP requests to be sent again, sl_NetAppArpFlush(), is supported on the CC3220.

    Regards,
    Michael

  • 0 in reply to Michael Reymond
    Expert 2545 points

    Hi Michael,

    Thanks for your prompt reply ! 

    I tried to reproduce, without success.

    It doesn't make sense for me either, because the DHCP server will not give an address which lease time hasn't elapsed. Maybe in special "STA disconnects" scenarios can the AP be releasing an IP (without updating the ARP table)? Just guessing here...

    I will get back to you with some NWP logs + wifi sniffing if I can reproduce. 

    In the meantime, we are calling the API sl_NetAppArpFlush() every 10s...

    Regards,

    VincenT