Brocade Virtual ADX Switch and Router Guide (Supporting ADX v03.1.00) - Manual (Page 123)

Brocade Virtual ADX Switch and Router Guide 109
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Configuring OSPF
6
Note regarding disabling OSPF
If you disable OSPF, the Layer 3 Switch removes all the configuration information for the disabled
protocol from the running-config. Moreover, when you save the configuration to the startup-config
file after disabling one of these protocols, all the configuration information for the disabled protocol
is removed from the startup-config file.
The CLI displays a warning message such as the following.
Virtual ADX(config-ospf-router)# no router ospf
router ospf mode now disabled. All ospf config data will be lost when writing to
flash!
If you have disabled the protocol but have not yet saved the configuration to the startup-config file
and reloaded the software, you can restore the configuration information by re-entering the
command to enable the protocol (ex: router ospf), or by selecting the Web management option to
enable the protocol. If you have already saved the configuration to the startup-config file and
reloaded the software, the information is gone.
If you are testing an OSPF configuration and are likely to disable and re-enable the protocol, you
might want to make a backup copy of the startup-config file containing the protocol’s configuration
information. This way, if you remove the configuration information by saving the configuration after
disabling the protocol, you can restore the configuration by copying the backup copy of the
startup-config file onto the flash 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 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. Type-7 External
LSAs are a special type of LSA generated only by ASBRs within an NSSA, and are flooded
to all the routers within only that NSSA.
• 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 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.