Brocade Communications Systems Layer 3 Routing Configuration ICX 6650 - Manual (Page 198)

180 Brocade ICX 6650 Layer 3 Routing Configuration Guide
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Configuring OSPF
• 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.
Example
To set up the OSPF areas shown in Figure 17 on page 169, enter the following commands.
Brocade(config-ospf-router)#area 192.168.1.0
Brocade(config-ospf-router)#area 10.5.0.0
Brocade(config-ospf-router)#area 192.168.0.0
Brocade(config-ospf-router)#area 0.0.0.0
Brocade(config-ospf-router)#write memory
Syntax: 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 a number, the number can be from 0 through 18.
NOTE
You can assign one area on a router interface. For example, if the system or chassis module has 16
ports, 16 areas are supported on the chassis or module.
Assigning a totally stubby area
By default, the Layer 3 Switch sends summary LSAs (LSA type 3) into stub areas. You can further
reduce the number of link state advertisements (LSAs) sent into a stub area by configuring the
Layer 3 Switch 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 Layer 3 Switch still accepts summary
LSAs from OSPF neighbors and floods them to other neighbors. The Layer 3 Switch 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 Layer 3 Switch flushes all of the summary
LSAs it has generated (as an ABR) from the area.