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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 115.
Table 115: 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 J-Web interface, select Configuration>View
and Edit>Edit Configuration.
- Next to Protocols, click Edit.
- Next to Ospf, click Edit.
|
From the [edit] hierarchy level, enter
edit protocols ospf
|
|
Set the external and internal route preferences.
|
- In the External preference box, type 130.
- In the Preference box, type the internal preference value
of 7.
- Click OK.
|
- Set the external preference:
set external-preference 130
- Set the internal preference:
set preference 7
|
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