Chapter 19
| Unicast Routing
Configuring the Open Shortest Path First Protocol (Version 2)
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◆ Originate Default Information – When the router is an NSSA Area Border
Router (ABR) or an NSSA Autonomous System Boundary Router (ASBR), this
option causes it to generate a Type-7 default LSA into the NSSA. This default
provides a route to other areas within the AS for an NSSA ABR, or to areas
outside the AS for an NSSA ASBR. (Default: Disabled)
An NSSA is similar to a stub, because when the router is an ABR, it can send a
default route for other areas in the AS into the NSSA using the Originate Default
Information option. However, an NSSA is different from a stub, because when
the router is an ASBR, it can import a default external AS route (for routing
protocol domains adjacent to the NSSA but not within the OSPF AS) into the
NSSA using this option.
◆ Metric Type – Type 1 or Type 2 external routes. When using Type 2, routers do
not add internal cost to the external route metric. (Default: Type 2)
◆ Metric – Metric assigned to Type-7 default LSAs. (Range: 0-16777214;
Default: 1)
◆ Default Cost – Cost for the default summary route sent into an NSSA from an
area border router (ABR). (Range: 0-16777215; Default: 0)
Note that when the default cost is set to “0,” the router will not advertise a
default route into the attached NSSA.
◆
Summary
–
Controls the use of summary routes. (Default: Summary)
■
Summary
–
Unlike stub areas, all Type-3 summary LSAs will be imported
into NSSAs to ensure that internal routes are always chosen over Type-7
NSSA external routes.
■
No Summary
–
Allows an area to retain standard NSSA features, but does
not inject inter-area routes (Type-3 and Type-4 summary routes) into this
area. Instead, it advertises a default route as a Type-3 LSA.
Web Interface
To configure protocol settings for an NSSA:
1. Click Routing Protocol, OSPF, Area.
2. Select Configure Area from the Step list.
3. Select Configure NSSA Area from the Action list.
4. Select a Process ID, and modify the routing behavior for an NSSA.
5. Click Apply
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