HP 200 Series Services And Applications page 127

Internet Protocol Routing Service
Static Routing
By default, the IP router uses manually configured static and/or default
routes in preference to routes gathered by protocol exchanges. You can
configure the preference for each static (conditional or nonconditional)
route as a weighted value used by the IP router to select from multiple
routes to a single destination. 0 is lowest preference; 16 is highest prefer-
ence. Routes with higher values will be selected for IP routing in preference
to routes with lower values.
Default Route
A default route is the path that a router directs a packet to when its routing
table does not contain the destination network specified in the packet's IP
header.
Upon receiving a packet, a router first compares the packet's destination
network against those found in its internal routing table. If the router finds
the destination network in its table, it directs the packet toward the corre-
sponding interface. If it doesn't, it directs the packet toward the interface
associated with the default route (providing one is configured) for further
processing by a neighboring router.
You can configure up to four default routes. By configuring multiple routes,
you ensure that a packet can be re-routed if the interface associated with the
default route is disabled.
You assign preference values (between 1 and 16, with 16 being the highest)
to each default route, to determine which default route gets the highest prior-
ity. If the highest priority default route is unavailable, the router uses the
next most-preferred default route. If this interface is also unavailable, the
router then chooses the next most-preferred default route. Should a disabled
default route with a higher priority value re-enable, the router uses it as the
default route.
For example, the figure 8 shows a sample multiple default route topology
and the preference values assigned to the four default routes. The IP router
directs packets addressed to networks A, B, or C through interfaces A, B,
and C. All other packets are directed to the default route D because it has
been assigned the highest preference among the default routes available. If
interface D becomes disabled, then the router uses default route E (and so
forth for default routes F and G).
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