Controlling Route Selection in the Forwarding Table

OSPF uses route preferences to select the route that is installed in the forwarding table when several routes have the same shortest path first (SFP) calculation. To evaluate a route, OSPF calculates the sum of the individual preferences of every router along the path and selects the route with the lowest total preference.

By default, internal OSPF routes have a preference value of 10, and external OSPF routes have a preference value of 150. Suppose all routers in your OSPF network use the default preference values. By setting the internal preference to 7 and the external preference to 130, you can ensure that the path through a particular Services Router is selected for the forwarding table any time multiple equal-cost paths to a destination exist.

To modify the default preferences on a Services Router:

1. Navigate to the top of the configuration hierarchy in either the J-Web or the CLI configuration editor.
2. Perform the configuration tasks described in Table 131.

Note: In general, we recommend not making changes to the default preference values. Changing preference values affects the router configuration, and can help to determine the active route.

Table 131: Controlling Route Selection in the Forwarding Table by Setting Preferences