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8.4 | ![]() |
Redistribution Example | |
8.4.3 | ![]() |
Phase 3: adding OSPF areas |
Each RIP domain can be converted into an
OSPF area independently of the other RIP domains. This allows the
migration of one section of the internetwork at a time, if desired.
When all three of the RIP domains have become OSPF areas, the three
core routers will serve as ABRs.
Notice that Figure
Because OSPF is classless, each ABR can be configured to use route summarization. For example, Router A connects to eight networks, which occupy a contiguous address space. Therefore, this ABR can be configured as follows to send a single supernet route, which will advertise all eight of the networks:
Router A will advertise one route, 172.16.8.0 255.255.255.0, which covers all subnets in Area 1, into Area 0. Without the range keyword in the area command, Router A would advertise each subnet individually. For example, one route for 172.16.8.0 255.255.255.0, one route for 172.16.9.0 255.255.255.0, and so forth. The migration of the network from RIP to OSPF is now complete, and redistribution is no longer necessary.
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