[j-nsp] Hidden and invisible routes

[Phill Jolliffe]

Interestingly you see a hidden route if the static route does a
recursive lookup. See config below and then show route output. The
nexthop interface for 10.0.21.2 is down when the below was executed.

This seems to show that at commit time , unless a static is set to
resolve via indirect next-hops, that the config parser checks for an
active, type direct, route in the same routing-instance that can
resolve statics next-hop. If non is found then the static is not, even
as a hidden, added to the routing-instance.

But if resolve is configured it is added persistently to the
routing-instance to allow routes that might become active in the
future to resolve it's indirect next hop and unhide it.

Makes sense? No point in keeping something in the table if it is not
allowed to be resolved indirectly and no interface can resolve it
directly. Though this would mean when a down interface come up that
this would have to trigger a check if the new direct type route cause
static routes in the config but not the routing-instance to become
resolvable.

[edit routing-options]
lab at w00t# run show route hidden

inet.0: 24 destinations, 25 routes (23 active, 0 holddown, 1 hidden)
+ = Active Route, - = Last Active, * = Both

2.3.4.0/24          [Static/5] 00:07:01
                      Unusable

[edit routing-options]
lab at w00t# show
static {
    route 1.0.0.0/8 next-hop 2.3.4.1;
    route 2.3.4.0/24 {
        next-hop 10.0.21.2;
        resolve;
    }
}

resolution {
    traceoptions {
        file foobar;
        flag all;
    }
}