Netgear XCM8806 Chassis User Manual - Page 678
Backbone Area Area 0.0.0.0, Stub Areas, Not-So-Stubby-Areas, to con an OSPF area as a stub area
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NETGEAR 8800 User Manual Backbone Area (Area 0.0.0.0) Any OSPF network that contains more than one area is required to have an area configured as area 0.0.0.0, also called the backbone. All areas in an AS must be connected to the backbone. When designing networks, you should start with area 0.0.0.0 and then expand into other areas. Note: Area 0.0.0.0 exists by default and cannot be deleted or changed. The backbone allows summary information to be exchanged between ABRs. Every ABR hears the area summaries from all other ABRs. The ABR then forms a picture of the distance to all networks outside of its area by examining the collected advertisements and adding in the backbone distance to each advertising router. When a VLAN is configured to run OSPF, you must configure the area for the VLAN. If you want to configure the VLAN to be part of a different OSPF area, use the following command: configure ospf vlan area If this is the first instance of the OSPF area being used, you must create the area first using the following command: create ospf area Stub Areas OSPF allows certain areas to be configured as stub areas. A stub area is connected to only one other area. The area that connects to a stub area can be the backbone area. External route information is not distributed into stub areas. Stub areas are used to reduce memory consumption and computational requirements on OSPF routers. Use the following command to configure an OSPF area as a stub area: configure ospf area stub [summary | nosummary] stub-default-cost Not-So-Stubby-Areas Not-so-stubby-areas (NSSAs) are similar to the existing OSPF stub area configuration option but have the following two additional capabilities: • External routes originating from an ASBR connected to the NSSA can be advertised within the NSSA. • External routes originating from the NSSA can be propagated to other areas, including the backbone area. The command line interface (CLI) command to control the NSSA function is similar to the command used for configuring a stub area, as follows: configure ospf area nssa [summary | nosummary] stub-default-cost {translate} 678 | Chapter 24. OSPF
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