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Margvin's avatar
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Apr 17, 2023

The Effect of Persistence on the Round Robin Method

HI F5 Warriors


I have a trouble from my costumer.Which in his server on the server he experiences very different traffic differences between their servers and in the F5 settings he has used the Round Robin method, but in the Persistance Source Address Affiliance profile, so how can the server be able to distribute traffic to the server evenly, due to info from the customer for the apps need persistence profile


Thanks for your help!!!

4 Replies

  • When the client connection is accepted, persistence entry have priority over the Load Balancing method. 
    So if an entry exists in the persistence table, F5 will send traffic to the real server that was bound with that entry. 
    This might lead to uneven traffic distribution, expecially if your clients are behind NAT, but it's the intended behavior. 


    To even out resource usage on your server farrm you might want to consider different load balancing methods instead of Round Robin, and use something dynamic instead. For example, F5 provides out-of-the-box connection-based or persistence-entry-based dynamic load distribution. details this further

    • Margvin's avatar
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      Thanks for the answer

      but which dynamic load balancing method is better to use for these conditions? because as you said that persistence has a higher entry value

      • CA_Valli's avatar
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        Do you have the possibility to try them out in a test plant before installing? Every environment is different from another and different method might perform better in some cases and worse in others. 

        Least Connections (node based) can be a "safe bet" if server farm is omogeneous and the goal is to even out traffic load. 
        I wouldn't go for session-based in this case since as I said sourceIP persistence doesn't really like NATs.

  • Is this an HTTP-based application? If so, and you are able to offload SSL to the VIP, try using cookie persistence instead of source IP persistence.

    With source IP persistence, if clients are traversing a forward proxy or have their source IP PAT'd to a single IP address, this may cause very uneven load distribution between the back-end servers. Coookie persistence doesn't have this problem as it doesn't use the source IP of the client.