Route Redistribution; Route Summarization - Cisco Nexus 3000 Series Configuration Manual

Information About OSPFv2
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 3 k - d o c f e e d b a c k @ c i s c o . c o m
Figure 3-4
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

OSPFv2 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. See
"Configuring Route Policy Manager,"
modify parameters in the AS External (type 5) and NSSA External (type 7) LSAs before these external
routes are advertised in the local OSPFv2 autonomous system.

Route Summarization

Because OSPFv2 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 10.1.1.0/24, 10.1.2.0/24, and
10.1.3.0/24 with one summary address, 10.1.0.0/16.
Typically, you would summarize at the boundaries of area border routers (ABRs). Although you could
configure summarization between any two areas, it is better to summarize in the direction of the
backbone so that the backbone receives all the aggregate addresses and injects them, already
summarized, into other areas. The two types of summarization are as follows:
•
•
You configure inter-area route summarization on ABRs, summarizing routes between areas in the
autonomous system. To take advantage of summarization, you should assign network numbers in areas
in a contiguous way to be able to lump these addresses into one range.
Cisco Nexus 3000 Series NX-OS Unicast Routing Configuration Guide, NX-OS Release 5.0(3)U1(1)
3-10
Virtual Links
ABR2
Inter-area route summarization
External route summarization
ABR1
1-6. You configure OSPFv2 to assign a link cost for these redistributed
for details on configuring route maps. You can use route maps to
Chapter 3 Configuring OSPFv2
Area 3
"Route
Chapter 11,