Virtual Links; Route Redistribution; Route Summarization - Cisco Nexus 7000 Series Configuration Manual

Information About OSPFv3
S e n d d o c u m e n t c o m m e n t s t o n e x u s 7 k - d o c f e e d b a c k @ c i s c o . c o m .

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.
through Area 5.
Figure 7-4
Area 0
Area 5
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
Redistribution" section on page
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
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.
Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.x
7-10
Figure 7-4 shows a virtual link that connects Area 3 to the backbone area
Virtual Links
ABR2
1-6. You configure OSPFv3 to assign a link cost for these redistributed
Chapter 16, "Configuring Route Policy Manager,"
ABR1
Chapter 7 Configuring OSPFv3
Area 3
"Route
for details on configuring
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