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Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.x
OL-20002-02
Chapter 7 Configuring OSPFv3
Information About OSPFv3
Virtual Links
Virtual links allow you to connect an OSPFv3 area ABR to a backbone area ABR when a direct physical
connection is not available. Figure 7-4 shows a virtual link that connects Area 3 to the backbone area
through Area 5.
Figure 7-4 Virtual Links
You can also use virtual links to temporarily recover from a partitioned area, which occurs when a link
within the area fails, isolating part of the area from reaching the designated ABR to the backbone area.
Route Redistribution
OSPFv3 can learn routes from other routing protocols by using route redistribution. See the “Route
Redistribution” section on page 1-6. You configure OSPFv3 to assign a link cost for these redistributed
routes or a default link cost for all redistributed routes.
Route redistribution uses route maps to control which external routes are redistributed. You must
configure a route map with the redistribution to control which routes are passed into OSPFv2. A route
map allows you to filter routes based on attributes such as the destination, origination protocol, route
type, route tag, and so on. You can use route maps to modify parameters in the AS External (type 5) and
NSSA External (type 7) LSAs before these external routes are advertised in the local OSPFv3
autonomous system. See Chapter 16, “Configuring Route Policy Manager,” for details on configuring
route maps.
Route Summarization
Because OSPFv3 shares all learned routes with every OSPF-enabled router, you might want to use route
summarization to reduce the number of unique routes that are flooded to every OSPF-enabled router.
Route summarization simplifies route tables by replacing more-specific addresses with an address that
represents all the specific addresses. For example, you can replace 2010:11:22:0:1000::1 and
2010:11:22:0:2000:679:1 with one summary address, 2010:11:22::/32.
ABR1
ABR2
Area 0
Area 3
Area 5
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