Alcatel Carrier Internetworking Solutions 060187-10 REV D Configuring Stub Area Default Metrics

Configuring OSPF Configuring OSPF

Configuring Stub Area Default Metrics

The default metric configures the type of cost metric that a default area border router (ABR) will advertise in the default summary Link State Advertisement (LSA). Use the ip ospf area default-metriccommand to create or delete a default metric for stub or Not So Stubby Area (NSSA) area. Specify the stub area and select a cost value or a route type, as shown:

-> ip ospf area 1.1.1.1 default-metric 0 cost 50

or

-> ip ospf area 1.1.1.1 default-metric 0 type type1

A route has a preset metric associated to it depending on its type. The first example, the stub area is given a default metric of 0 (this is Type of Service 0) and a cost of 50 added to routes from the area. The second example specifies that the cost associated with Type 1 routes should be applied to routes from the area.

Note. At this time, only the default metric of ToS 0 is supported.

To remove the area default-metric setting, enter the ip ospf area default-metriccommand using the no command, as shown:

-> no ip ospf area 1.1.1.1 default-metric 0

Setting Area Ranges

Area ranges are used to summarize many area routes into a single advertisement at an area boundary. Ranges are advertised as summaries or NSSAs. Ranges also act as filters that either allow the summary to be advertised or not. Ranges are created using the ip ospf area range command. An area and the summary IP address and IP mask must be specified. For example, to create a summary range with IP address

192.5.40.1and an IP mask of 255.255.255.0 for area 1.1.1.1, the following commands would be entered at the CLI prompt:

-> ip ospf area 1.1.1.1 range summary 192.5.40.1 255.255.255.0

-> ip ospf area 1.1.1.1 range summary 192.5.40.1 255.255.255.0 effect noMatching

To view the configured ranges for an area, use the show ip ospf area range command as demonstrated:

-> show ip ospf area 1.1.1.1 range

Configuring a Totally Stubby Area

In order to configure a totally stubby area you need to configure the area as stub on the ABR and disable summarization. By doing so the ABR will generate a default route in the totally stubby area. In addition, the other routers within the totally stubby area must only have their area configured as stub.

For example, to configure the simple totally stubby configuration shown in the figure in “Configuring a Totally Stubby Area” on page 1-20where Router B is an ABR between the backbone area 0 and the stub area 1 and Router A is in Totally Stubby Area 1.1.1.1 follow the steps below:

page 1-20 OmniSwitch 6600 Family Advanced Routing Configuration Guide March 2005