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Emil_Tr's avatar
Emil_Tr
Icon for Altostratus rankAltostratus
Jan 22, 2025

GARP when changing partition's traffic group

When changing partitions traffic group, a GARP sent.

I need the complete list of which GARP objects are sent? (VSs, Self IPs, etc..)

Note: I use MAC Masquerade on both traffic groups I have. 

  • f51's avatar
    f51
    Icon for Cirrocumulus rankCirrocumulus

    Hello Emil,

    When a traffic group in F5 BIG-IP is moved from one device to another, Gratuitous ARP (GARP) messages are sent to inform the network about the new location of the IP addresses associated with the traffic group. This helps in updating the ARP tables of the connected devices, ensuring that traffic is directed to the correct device. The GARP messages are sent for various network objects associated with the traffic group.

    Here is a list of the objects for which GARP messages are typically sent when changing a partition's traffic group:

    1. Virtual Servers (VSs): All virtual servers associated with the traffic group will send GARP messages for their IP addresses.
    2. Self IPs: Self IP addresses associated with the traffic group will send GARP messages. These are the IP addresses that the F5 uses to communicate with other network devices.
    3. Floating IPs: Any floating IP addresses assigned to the traffic group will send GARP messages. Floating IPs are shared between devices in a device group and move with the traffic group.
    4. SNAT (Source Network Address Translation) Addresses: If there are any SNAT addresses associated with the traffic group, GARP messages will be sent for these as well.
    5. MAC Masquerade Addresses: Since you mentioned that MAC Masquerade is used, GARP messages will be sent for the MAC Masquerade addresses. This helps in ensuring that the MAC address associated with the traffic group is updated across the network.

    The GARP messages help in ensuring that all connected devices are aware of the new owner of the IP addresses, preventing any disruption in traffic flow. The use of MAC Masquerade further helps in maintaining consistent network behavior by ensuring that the MAC address remains the same even if the traffic group moves to a different device.

    Refer Below Articles

    https://my.f5.com/manage/s/article/K13502

    https://my.f5.com/manage/s/article/K13881

     

  • Hi

    Thank you for your reply. I was asking about changing a partition's traffic group, not traffic group active device change.

    By the way, if I understand correctly , with MAC Masquerade the MAC does not change when traffic group switching between devices, so no GARP needed

  • f51's avatar
    f51
    Icon for Cirrocumulus rankCirrocumulus

    Thank you for the clarification. You are correct; when using MAC Masquerade, the MAC address does not change when a traffic group switches between devices, which minimizes the need for GARPs. However, when you change the traffic group of a partition, GARPs are still involved to inform the network about the new IP-to-MAC address mappings.