Brocade Virtual ADX Switch and Router Guide (Supporting ADX v03.1.00) - Manual (Page 168)

154 Brocade Virtual ADX Switch and Router Guide
53-1003246-01
Enabling OSPFv3
7
• 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 LSAs 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 Autonomous System (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, OSPFv3 elects one of the ABRs to perform
the LSA translation for the NSSA. OSPF elects the ABR with the highest router ID. If the
elected ABR becomes unavailable, OSPFv3 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 OSPFv3 areas 0.0.0.0, 200.5.0.0, 192.5.1.0, and 195.5.0.0, enter the following
commands:
Virtual ADX(config-ospf6-router)# area 0.0.0.0
Virtual ADX(config-ospf6-router)# area 200.5.0.0
Virtual ADX(config-ospf6-router)# area 192.5.1.0
Virtual ADX(config-ospf6-router)# area 195.5.0.0
Syntax: [no] area number | ipv4-address
The number | ipv4-address parameter specifies the area number, which can be a number or in
IPv4 address format. If you specify a number, the number can be from 0 through 2,147,483,647.
NOTE
You can assign only one area on a router interface.
NOTE
By default, the Brocade router ID is the IPv4 address configured on the lowest numbered loopback
interface. If the Brocade device does not have a loopback interface, the default router ID is the
lowest numbered IPv4 address configured on the device.
Assigning an NSSA area
The OSPF NSSA feature enables you to configure OSPF areas that provide the benefits of stub
areas, but are also capable of importing external route information. OSPF does not flood external
routes from other areas into an NSSA, but does translate and flood route information from the
NSSA into other areas, such as the backbone.
NSSAs are especially useful when you want to summarize Type 5 External LSAs (external routes)
before forwarding them into an OSPF area. The OSPF specification (RFC 2328) prohibits
summarization of Type 5 LSAs and requires OSPF to flood Type 5 LSAs throughout a routing
domain. When you configure an NSSA, you can specify an address range for aggregating the
external routes that the ABR of the NSSAs exports into other areas.