Note regarding disabling OSPF
If you disable OSPF, the device removes all the conguration information for the disabled protocol from the running conguration.
Moreover, when you save the conguration to the startup conguration le after disabling one of these protocols, all the conguration
information for the disabled protocol is removed from the startup conguration le.
The CLI displays a warning message such as the following.
device(config-ospf-router)# no router ospf
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
conguration to the startup conguration le and reloaded the software, you
can restore the conguration information by re-entering the router ospf command or by selecting the Web management option to
enable the protocol. If you have already saved the conguration to the startup conguration le and reloaded the software, the
information is gone.
If you are testing an OSPF conguration and are likely to disable and re-enable the protocol, you might want to make a backup copy of
the startup conguration le containing the protocol’s conguration information. This way, if you remove the conguration information by
saving the conguration after disabling the protocol, you can restore the conguration by copying the backup copy of the startup
conguration le onto the ash memory.
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 (subnets) on a router port. Each port on a router can support one area.
An area can be normal, a stub, or a Not-So-Stubby Area (NSSA) :
• Normal - OSPF routers within a normal area can send and receive External Link State Advertisements (LSAs).
• Stub - OSPF routers within a stub area cannot send or receive External LSAs. In addition, OSPF routers 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 trac 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. Type-7 External LSAs are a special type of LSA
generated only by ASBRs within an NSSA, and are ooded to all the routers within only that NSSA.
– ABRs translate type 7 LSAs into type 5 External LSAs, which can then be ooded throughout the AS. You can congure
address ranges on the ABR of an NSSA so that the ABR converts multiple type-7 External LSAs received from the NSSA
into a single type-5 External LSA.
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.
To set up the OSPF areas use the following method.
device(config-ospf-router)# area 192.5.1.0
device(config-ospf-router)# area 200.5.0.0
device(config-ospf-router)# area 195.5.0.0
device(config-ospf-router)# area 0.0.0.0
device(config-ospf-router)# write memory
Syntax: [no] area { num | ip-addr }
The num and ip-addr parameters specify the area number, which can be a number or in IP address format. If you specify a number, the
number can be from 0 - 2,147,483,647.
Conguring OSPF
FastIron Ethernet Switch Layer 3 Routing
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