Implementing a Scalable Multiarea Network OSPF-Based Solution Lab 3-4 Debrief Implementing a Scalable Multiarea Network OSPF-Based Solution

Lab Topology

Lab Review: What Did You Accomplish? Task 1: Examining OSPF Routing Information How can you verify the operation of an OSPF routing protocol? What you can see by observing OSPF neighbors, the OSPF database, OSPF interfaces, and the IP routing table? Task 2: Optimizing OSPF Routing for Area 24 What steps are required to restrict OSPF from announcing information about OSPF external routers, while preserving the insertion of internal routes from other areas? Task 3: Minimizing OSPF Information in Area 24 What steps are also required to restrict OSPF from announcing information about OSPF internal routers from other OSPF areas?

Lab Review: What Did You Accomplish? (Cont.) Task 4: Reducing OSPF Information in Area 3 What steps are required to minimize the sizes of the OSPF link-state database and IP routing table on a router inside the area in such a way that only information about the area announced routes (internal or external) is allowed and redistribution of external routes is preserved.

Verification Did you have enough information to create an implementation plan? Were you able to define the OSPF topology and content of the IP routing table? After task 2, were external routes from other areas are suppressed and internal routes, while internal routes remained in the IP routing table and were injectable? After task 3, were external and internal routes from other areas suppressed? After task 4, were external and internal routes from other areas prevented from being injected, while redistribution of external routes was allowed?

Checkpoints Examine the IP routing information exchanged by routers configured with the OSPF routing protocol. Change the area type to suppress external routes from other areas to be injected. Check the IP routing table and OSPF database for verification. Change the area type to suppress external and internal routes from other areas to be injected. Change the area type to suppress external and internal routes but allow the injection of external routes into the area.

A Sample Solution The IP routing table is verified for OSPF routes. The existing configuration of the area type for area 24 has been changed from normal to stub and then to totally-stubby in order to manipulate the insertion of routes into the area. The existing configuration for area 3 has been changed to a totally not-so-stubby (NSSA) area in order to manipulate the insertion of routes into the area.

Alternative Solutions Summarization and filtering can be used in order to manipulate the insertion of routes into a specific area. Because changing the routing protocol is not a realistic solution, you can implement static and default routes with filtering instead.

Q and A How you can verify OSPF routes and the OSPF topology? What can you change in OSPF to manipulate which routes are inserted into an area? Which OSPF area type suppresses external routes from other areas to be inserted? Which OSPF area type suppresses external and internal routes from other areas to be inserted? Which area type suppresses external routes from other areas to be inserted, but allows redistribution of external routes? Which area type suppresses external and internal routes from other areas to be inserted, but allows redistribution of external routes?

Summary The IP routing table provides information that can be used to verify the proper configuration of different OSPF area types. To optimize OSPF you must configure area 24 as an OSPF stub area. To minimize OSPF information in area 24, you must configure an OSPF totally-stub area. To reduce OSPF information in area 3, you must configure an OSPF totally not-so-stubby (NSSA) area.