Brocade BigIron RX Series Configuration Guide - Manual (Page 840)

762 BigIron RX Series Configuration Guide
53-1002484-04
Configuring OSPF
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• 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.
To set up the OSPF areas shown in Figure 111 on page 754, use the following method.
BigIron RX(config-ospf-router)# area 192.5.1.0
BigIron RX(config-ospf-router)# area 200.5.0.0
BigIron RX(config-ospf-router)# area 195.5.0.0
BigIron RX(config-ospf-router)# area 0.0.0.0
BigIron RX(config-ospf-router) write memory
Syntax: [no] area <num> | <ip-addr>
The <num> | <ip-addr> parameter specifies the area number, which can be a number or in IP
address format. If you specify an number, the number can be from 0 – 2,147,483,647.
Assign a totally stubby area
By default, the device sends summary LSAs (LSA type 3) into stub areas. You can further reduce
the number of link state advertisements (LSA) sent into a stub area by configuring the device to
stop sending summary LSAs (type 3 LSAs) into the area. You can disable the summary LSAs when
you are configuring the stub area or later after you have configured the area.
This feature disables origination of summary LSAs, but the device still accepts summary LSAs from
OSPF neighbors and floods them to other neighbors. The device can form adjacencies with other
routers regardless of whether summarization is enabled or disabled for areas on each router.
When you enter a command to disable the summary LSAs, the change takes effect immediately. If
you apply the option to a previously configured area, the device flushes all of the summary LSAs it
has generated (as an ABR) from the area.
NOTE
This feature applies only when the BigIron RX is configured as an Area Border Router (ABR) for the
area. To completely prevent summary LSAs from being sent to the area, disable the summary LSAs
on each OSPF router that is an ABR for the area.
This feature does not apply to Not So Stubby Areas (NSSAs).
To disable summary LSAs for a stub area, enter commands such as the following.
BigIron RX(config-ospf-router)# area 40 stub 99 no-summary
Syntax: [no] area <num> | <ip-addr> stub <cost> [no-summary]
The <num> | <ip-addr> parameter specifies 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.