Configuring OSPF
Note Regarding Disabling OSPF
If you disable OSPF, the routing switch removes all the configuration information for the disabled protocol from the
The CLI displays a warning message such as the following:
router ospf mode now disabled. All ospf config data will be lost when writing to flash!
The Web management interface does not display a warning message.
If you have disabled the protocol but have not yet saved the configuration to the
If you are testing an OSPF configuration and are likely to disable and
Assign OSPF Areas
Once OSPF is enabled on the system, you can assign areas. Assign an IP address or number as the area ID for each area. The area ID is representative of all IP addresses
An area can be normal, a stub, or a
•Normal – OSPF routing switches within a normal area can send and receive External Link State Advertisements (LSAs).
•Stub – OSPF routing switches within a stub area cannot send or receive External LSAs. In addition, OSPF routing switches in a stub area must use a default route to the area’s Area Border Router (ABR) or Autonomous System Boundary Router (ASBR) to send traffic out of the area.
•NSSA – The ASBR of an NSSA can import external route information into the area.
•ASBRs redistribute (import) external routes into the NSSA as type 7 LSAs.
•ABRs translate type 7 LSAs into type 5 External LSAs, which can then be flooded throughout the AS. You can configure address ranges on the ABR of an NSSA so that the ABR converts multiple
When an NSSA contains more than one ABR, OSPF elects one of the ABRs to perform the LSA translation for NSSA. OSPF elects the ABR with the highest router ID. If the elected ABR becomes unavailable, OSPF automatically elects the ABR with the next highest router ID to take over translation of LSAs for the NSSA. The election process for NSSA ABRs is automatic.
EXAMPLE:
To set up the OSPF areas shown in Figure 8.1 on page
USING THE CLI
Syntax: area <num>
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