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BabaG's avatar
BabaG
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Sep 12, 2019

Failover require to clear manually ARPs in other networks devices to converge

Hello guys,

 

This may sounds not F5 issue, but i just need to clarity if anyone has come across issue like this

One of our Engineer is replacing host VCMP  replacement of 2150 blade with 2250 as well as code upgrade from 12.00 to 12.1.1, am guessing.

"Every time that we make a failover, we have to clear manually ARP in other networks devices, like routers or other devices along the paths that participating in caches ARPs."

 

If do require any more information please let me know.

  • youssef1's avatar
    youssef1
    Icon for Cumulonimbus rankCumulonimbus
    Sep 12, 2019

    Hi,

     

    indeed you must have a problem on your network equipment. When a redundant BIG-IP system moves to an active status for a traffic group (faillover trigged), the system broadcasts a series of gratuitous ARP (GARP) packets to the network to update ARP tables on directly connected network devices or hosts.

     

    If you do a TCPDUMP on member that will be active you can see all this gratuitous ARP. and you can proof that F5 do the job correctly.

     

    however you must pay attention to a point, I already had a similar problem because I had too many VS and so many ARPs that are submitted to the network. Some routers / switches are limited and ignore part of the Freeous ARP. there is a configuration to solve this problem, I could provide it to you if you are in this case.

     

    how many vs do you have on your f5?

     

    regards

  • BabaG's avatar
    BabaG
    Icon for Nimbostratus rankNimbostratus
    Sep 12, 2019

    Thanks for quick reply, I have never come across issues of failing one device and causes downstream devices to misbehaving. I was at this point thinking arps caching time on the downstream devices could be the issue, therefore everything you have analysed and suggested could be culprit.

    We have over 10 Vs from what I know but it could be more

     

    Yes, would like to see suggested solutions or workaround to resolve the issue.

     

    Many Thanks

     

    Baba

  • youssef1's avatar
    youssef1
    Icon for Cumulonimbus rankCumulonimbus
    Sep 12, 2019

    before going further you must target the problem.

    So make a trace and check that F5 submits the gratuitous arp, you have all information needed in the following post, you have also several solutions describe:

     

    https://devcentral.f5.com/s/question/0D51T00006j3Ba9/f5-gratuitousarp-issue-when-failover

     

    just a little simple check. Did you check that arp is enable in your VS?

     

    Local Traffic  ››  Virtual Servers : Virtual Address List

    then clienck on each IP and check thar APR is enabled.

     

    And in your Device Group you selected Group Type: sync and failover.

     

    Regards,