[j-nsp] Two default Routes

[Jonathan Looney]

Peder,

By default, the software chooses a single next-hop for every prefix in
the routing table and installs just that next-hop in the forwarding
table.  So, in the case of a default route, everything following that
default route will go to the same next-hop.

If you want to do any kind of load-balancing between multiple
next-hops, you need to apply a policy to the forwarding table to cause
multiple next-hops to be used (by using the "then" "load-balance
per-packet" statement).

For example, the following will cause multiple next-hops to be
installed in the forwarding table:

routing-options {
    forwarding-table {
        export load-balance-default;
    }
}
policy-options {
    policy-statement load-balance-default {
        term default-route {
            from {
                route-filter 0.0.0.0/0 exact;
            }
            then {
                load-balance per-packet;
            }
        }
    }
}

The particular behavior this will cause is platform-dependent.  On
some platforms, it will cause per-packet load balancing.  On others,
it will cause per-flow load balancing.  You can see the "Configuring
Per-Packet Load Balancing" section of the JUNOS "Routing Protocols
Configuration Guide" for more information.

HTHs,
Jon


On 8/17/06, Peder @ NetworkOblivion <peder at networkoblivion.com> wrote:
> I think I've seen this discussed before, but I googled and can't get the
> right keywords.  How does a Juniper J series (or any Juniper for that
> matter) handle multiple default routes (or multiple static routes with
> the same metric)?  Does it do packet by packet?  Or flow-based?  Or neither?
>
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