1 / 15

Implementing a Scalable Multiarea Network OSPF-Based Solution

Configuring and Verifying OSPF Route Summarization. Implementing a Scalable Multiarea Network OSPF-Based Solution. Summarization. Networks are normally translated into type 3 LSAs in other areas. Route summarization is the consolidation of advertised addresses.

orrin
Download Presentation

Implementing a Scalable Multiarea Network OSPF-Based Solution

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Configuring and Verifying OSPF Route Summarization Implementing a Scalable Multiarea Network OSPF-Based Solution

  2. Summarization • Networks are normally translated into type 3 LSAs in other areas. • Route summarization is the consolidation of advertised addresses. • On ABR, summarize type 3 LSAs • On ASBR, summarize type 5 LSAs • A good addressing plan is required. • A drawback is the possibility of suboptimal routing.

  3. Benefits of Route Summarization • Minimizes the number of routing table entries • Localizes the impact of a topology change • Reduces LSA flooding and saves CPU resources

  4. Interarea Route Summarization • A summary route will be generated if at least one subnet within the area falls in the summary address range. • A summarized route metric will be equal to the lowest cost of all subnets within the summary address range. • Only for the summary routes of connected areas: • The ABR creates a route to Null 0 to avoid loops.

  5. Using Route Summarization • Interarea summary link carries a mask • One or more entries can represent several subnets

  6. Configure Interarea Route Summarization • Configures type 3 summarization on ABRs

  7. Route Summarization Configuration Example at the ABR

  8. External Route Summarization • Summarization can be used for external routes: • on an AS boundary for type 5 LSAs (redistributed routes) • on an NSSA ABR for type 5 translated from type 7 • A summary route to Null 0 will be created for each summary range

  9. Configure External Route Summarization • Configures type 5 summarization of redistributed routes on ASBRs

  10. Route Summarization Configuration Example at ASBR

  11. Default Routes in OSPF • A default route is injected into OSPF as an external type 5 LSA. • Default route distribution is not on by default. • Benefits of default routes include: • A smaller routing table • Fewer resources used in the router

  12. Configure OSPF Default Route • The first command allows the ASBR to originate a type 5 default route if it has the gateway of last resort. • The second command allows the ASBR to originate a type 5 default route even if there is no gateway of last resort (optional). • Use the route map to define a dependency on any condition inside the route map (optional).

  13. Default Route Configuration Example

  14. Summary • Route summarization improves CPU utilization, reduces LSA flooding, and reduces routing table sizes. • The area range command is used to summarize at the ABR. The summary-address command is used to summarize at the ASBR. • Default routes can be used in OSPF to prevent the need for a specific route to each destination network. The benefits include a much smaller routing table and an LSDB with complete reachability. • OSPF uses the default-information originate command to inject a default route.

More Related