Routing Protocol Preference

This section describes the preferences of all the routing protocols.

Routing protocols (including the static route) can learn different routes to the same destination, but not all routes are optimal. Only one routing protocol at one time determines the optimal route to a destination. To select the optimal route, each routing protocol (including the static route) is configured with a preference (the smaller the value, the higher the preference). When multiple routing information sources coexist, the route with the highest preference is selected as the optimal route (the smaller the value is, the higher the preference is). Table 1 lists the routing protocols and the default preferences of routes found by each protocol.

In Table 1, 0 indicates the direct route, and 255 indicates any route learned from unreliable sources.

Except for direct routes, you can manually configure a routing protocol's preference. In addition, the preference for each static route can be distinct from the other routes.

The FW also defines the external preference and internal preference. External preference is the preference set by a user for each routing protocol. Table 1 shows the default external preference.

If different routing protocols are configured with the same preference, the system determines which routes discovered by these routing protocols become the preferred routes through an internal preference. Table 2 shows the internal preferences of routing protocols.

For example, two routes, an OSPF route and a static route, can reach the destination 10.1.1.0/24, and the preferences of both routes are set to 5. In this case, the FW determines the optimal route according to the internal preferences listed in Table 2. The internal preference value 10 of OSPF is higher than the internal preference value 60 of the static route. Therefore, the system selects the route discovered by OSPF as the optimal route.