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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:
- Navigate to the top of the configuration hierarchy
in either the J-Web or the CLI configuration editor.
- Perform the configuration tasks described in Table 50.
Table 50: Controlling Route
Selection in the Forwarding Table by Setting Preferences
|
Task
|
J-Web Configuration Editor
|
CLI Configuration Editor
|
|
Navigate to the Ospf level in the configuration
hierarchy.
|
In the configuration editor hierarchy, select Protocols>Ospf.
|
From the top of the configuration hierarchy, enter
edit protocols ospf
|
|
Set the external and internal route preferences.
|
- In the External preference box, type an external preference
value—for example, 7.
- In the Preference box, type an internal preference value—for
example, 130.
- Click OK.
|
- Set the internal preference. For example:
set preference 7
- Set the external preference. For example:
set external-preference 130
Changes in the CLI are applied automatically when you execute the set command.
|
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