R21xx-HP FlexFabric 11900 Layer 3 IP Routing Configuration Guide

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Route preference
Routing protocols, including static and direct routing, each by default have a preference. If they find
multiple routes to the same destination, the router selects the route with the highest preference as the
optimal route.
The preference of a direct route is always 0 and cannot be changed. You can configure a preference for
each static route and each dynamic routing protocol. The following table lists the route types and default
preferences. The smaller the value, the higher the preference.
Table 3 Route types and default route preferences
Route type Preference
Direct route 0
Multicast static route 1
OSPF 10
IS-IS 15
Unicast static route 60
RIP 100
OSPF ASE 150
OSPF NSSA 150
IBGP 255
EBGP 255
Unknown (route from an untrusted source) 256
Load sharing
A routing protocol may find multiple optimal equal-cost routes to the same destination. You can use these
routes to implement equal-cost multi-path (ECMP) load sharing.
Static routing, IPv6 static routing, RIP, RIPng, OSPF, OSPFv3, BGP, IPv6 BGP, IS-IS, and IPv6 IS-IS support
ECMP load sharing.
Route backup
Route backup can improve network availability. Among multiple routes to the same destination, the route
with the highest priority is the primary route and others are secondary routes.
The router forwards matching packets through the primary route. When the primary route fails, the route
with the highest preference among the secondary routes is selected to forward packets. When the
primary route recovers, the router uses it to forward packets.