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Configuring OSPF route control
This section covers how to control OSPF routing information advertisement and reception, and
route redistribution from other protocols.
Prerequisites
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IP addresses for interfaces
•
OSPF functions
•
Corresponding filters, if routing information filtering is needed
Configuring OSPF route summarization
Route summarization is when an ABR or ASBR summarizes routes with the same prefix into a
single route and distributes it to other areas.
Through route summarization, routing information across areas and the size of routing tables on
routers will be reduced, improving the calculation speed of routers.
Assume in an area are three internal routes: 19.1.1.0/24, 19.1.2.0/24, and 19.1.3.0/24. By
configuring route summarization on the ABR, the three routes are summarized into the route
19.1.0.0/16 that is advertised into other areas.
Configuring route summarization on an ABR
If contiguous network segments are available in the area, you can summarize them into a single
network segment. An ABR generates Type-3 LSAs on a per network segment basis for an attached
non-backbone area.
In this way, the ABR in the area distributes only the summary LSA to reduce the scale of LSDBs on
routers in other areas and the influence of topological changes.
To do…
Use the command…
Remarks