SRX

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  • 1.  per-prefix load balancing

    Posted 01-22-2010 08:20

    what's the difference between these commands?

     

    set forwarding-options load-balance per-prefix

     

    -and-

     

    set policy-options policy-statement DestinationLoadBalance then load-balance per-packet

    set routing-options forwarding-table export DestinationLoadBalance

     

    ?

     

    jtac indicates that the policy-options/export is the best way to load balance connections over multiple links on a prefix basis, but the rules and the manual seem to indicate that it will load balance on a packet, not destination (prefix) basis.

     

    either seem to work (with a limited set of testing machines).

     

     



  • 2.  RE: per-prefix load balancing
    Best Answer

    Posted 01-22-2010 10:13

    By default, the JUNOS software uses a hashing method based only on the destination address to elect a forwarding next hop when multiple equal-cost paths are available. As a result, when multiple routers share the same set of forwarding next hops for a given destination, they can elect the same forwarding next hop.

     

    when we have a route with a protocol next hop that is not directly connected, it can be resolved over a set of equal-cost forwarding next hops. Only in this case, we use the hashing algorithm to elect a forwarding next hop. An example of this is routes learned from an IBGP neighbor. The protocol next hop for those routes might not be directly reachable and would be resolved through some IGP or static routes. The result could be a set of equal-cost forwarding next hops to reach that protocol next hop. Per-prefix load balancing thus leads to better utilization of the available links.

    To configure per-prefix load balancing. include the load-balance statement at the [edit forwarding-options] hierarchy level:

    [edit forwarding-options] load-balance { indexed-next-hop; per-prefix { hash-seed number; } } To enable per-prefix load balancing, you must include the hash-seed number statement.



  • 3.  RE: per-prefix load balancing

    Posted 01-22-2010 13:51

     

    @John_Burns wrote:

    Per-prefix load balancing thus leads to better utilization of the available links.

    To configure per-prefix load balancing. include the load-balance statement at the [edit forwarding-options] hierarchy level:

    [edit forwarding-options] load-balance { indexed-next-hop; per-prefix { hash-seed number; } } To enable per-prefix load balancing, you must include the hash-seed number statement.

     

     

    based on this, then the bast of the two commands is:

     

    set forwarding-options load-balance per-prefix hash-seed 12345

     

     

    not certain why jtac is recommending the other, but i'll update my config.

     

    thanks!