Load Sharing; Route Backup; Route Recursion - HP 6125G Configuration Manual

The preference of a direct route is always 0 and cannot be changed. You can manually configure
preferences for any other route type. Each static route can be configured with a different preference. The
following table lists the types of routes and the default preferences. The smaller the preference value, the
higher the preference.
Table 3 Route types and their default route preferences
Routing approach
Direct route
OSPF
Static route
RIP
OSPF ASE
OSPF NSSA
IBGP
EBGP
Unknown (route from an untrusted source)

Load sharing

A routing protocol can be configured with multiple equal-cost routes to the same destination. These routes
have the same preference and will all be used to accomplish load sharing if there is no route with a
higher preference available.
Static routing/IPv6 static routing, RIP/RIPng, OSPF/OSPFv3, and BGP/IPv6 BGP supports ECMP load
sharing.

Route backup

Route backup can improve network availability. Among multiple routes to the same destination, the route
with the highest preference is the main route and all others are backup routes.
The router forwards matching packets through the main route. When the main route fails, the route with
the highest preference among the backup routes is selected to forward packets. When the main route
recovers, the router uses it to forward packets.

Route recursion

To use a BGP route, static route (that is configured with a next hop but with no output interface), or RIP
route that has an indirectly-connected next hop, a router must perform route recursion to find the outgoing
interface to reach the next hop.
Link-state routing protocols, such as OSPF, do not need route recursion, because they obtain
directly-connected next hops through route calculation.
Preference
0
10
60
100
150
150
255
255
256
3