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  1. Hi Rene,
    Thanks for your very nice article.
    Please clarify ""If we use different hashing algorithm then the flow will be considered based on different parameter but same flow will use the same link,Not possible any load balance using different hashing algorithm , right ??? and if we use "ip load-sharing per-packet" at interface level then all packet will push across all available link . we can influence Load Balance , right ??
    So In summary.........
    1. Different hashing algorithm : Only flow will be consider based on different parameter like Src IP/dst IP/L4 Port etc.
    2. ip load-sharing per-packet at interface level : Per-Packet will be load balance across all link even though the packets are belong to same flow .

    br//zaman

  2. Hi Zaman,

    What I mean by this is that for a single flow, the router always selects the same interface no matter the hash algorithm you use. The advantage of using a hash algorithm that uses more parameters is that you will have better load balancing since different flows will use different interfaces. For example, if you use a hashing algorithm that only includes source and destination IP address then it's likely that the following flows will all get the same result and use the same outbound interface.

    Here's a quick example, let's say we have these flows:

    192.168.1.1 > 192.168.2.2
    192.168.1.2 > 192.168.2.2
    192.168.1.3 > 192.168.2.2
    192.168.1.4 > 192.168.2.2
    192.168.1.5 > 192.168.2.2
    192.168.1.7 > 192.168.2.2
    192.168.1.9 > 192.168.2.2

    If we had two outgoing interfaces, it would be nice to see 4 flows on each interface so that we have some load sharing. However in reality, it's likely that the flows get mapped like this:

    INTERFACE 1:

    192.168.1.1 > 192.168.2.2
    192.168.1.3 > 192.168.2.2
    192.168.1.5 > 192.168.2.2
    192.168.1.7 > 192.168.2.2
    192.168.1.9 > 192.168.2.2

    INTERFACE 2:

    192.168.1.2 > 192.168.2.2
    192.168.1.4 > 192.168.2.2

    In this case, interface 1 gets the most flows. By using a hashing algorithm with more parameters, the chance that each interface gets 50% of the flows increases. Still, this doesn't consider how much traffic each flow has so it's more like "flow" balancing than load balancing :slight_smile:

    Per packet load balancing does evenly share the load, even though the packets belong to the same flow yes.

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