H3C Technologies H3C WX6000 Series Access Controllers - Manual (Page 206)

21-4
Routing Protocols and Routing Priority
Different routing protocols may find different routes to the same destination. However, not all of those
routes are optimal. In fact, at a particular moment, only one protocol can uniquely determine the current
optimal routing to the destination. For the purpose of route selection, each routing protocol (including
static routes) is assigned a priority. The route found by the routing protocol with the highest priority is
preferred.
The following table lists some routing protocols and the default priorities for routes found by them:
Routing approach Priority
DIRECT 0
OSPF 10
IS-IS 15
STATIC 60
RIP 100
OSPF ASE 150
OSPF NSSA 150
IBGP 255
EBGP 255
UNKNOWN 256
z
The smaller the priority value, the higher the priority.
z
The priority for a direct route is always 0, which you cannot change. Any other type of routes can
have their priorities manually configured.
z
Each static route can be configured with a different priority.
z
IPv4 and IPv6 routes have their own respective routing tables.
Route backup
Route backup can help improve network reliability. With route backup, you can configure multiple routes
to the same destination, expecting the one with the highest priority to be the main route and all the rest
backup routes.
Under normal circumstances, packets are forwarded through the main route. When the main route goes
down, the route with the highest priority among the backup routes is selected to forward packets. When
the main route recovers, the route selection process is performed again and the main route is selected
again to forward packets.