9tut new ccna

9tut new ccna.Backbone area A special OSPF area to which all other areas must be connected - Area 0Intra-area routing This route arrives at a subnet that is in the same area as the routerInter-area routing This route arrives on a subnet that is not in the same area as the router4.2 Basic content 168How Zones Reduce SPF Computation Time Figure 8-7 shows a sample zone design and some of the terminology associated with zones, but it does not show the capabilities and benefits of zones. To understand how regions reduce the work that SPF must do, you need to understand what the region design makes happen to the LSDBs in the region. most of the processing time for SPF is spent dealing with all the topology details. i.e., the routers and links that connect the routers. Regions reduce the workload of SPF because, for a given region, the LSDB lists only the routers and links within that region, as shown on the left side of Figure 8-8. Region 1 LSDBFigure 8-8 Smaller Area 1LSDB ConceptAlthough an LSDB has less topology information, it must still have information about all subnets in all areas so that each router can create IPv4 routes for all subnets. By area design, OSPFv2 uses very brief summary information about subnets in other areas. These LSAs do not include topology information for other areas, so they do not require extensive SPF processing at all. Instead, these subnets all look like subnets connected to an ABR (in this case ABRD1). Advantages of OSPF Region DesignIn summary, using a single-region OSPF design is suitable for smaller OSPF networks. It avoids the added complexity and makes the network slightly easier to operate. It also requires less planning effort, as there is no need to plan which part of the network will end up in which region. For larger networks, using multiple regions can improve OSPF operations in many ways. The following list summarizes some key points about whether multiple regions should be used in larger OSPF networks. ,. Words*. Smaller per-region LSDBs require less memory.1. bong. Routers require fewer CPU cycles to process smaller per-region LSDBs using the SPF algorithm. reducing CPU overhead and improving convergence times.... Changes in the network (for example, link failures and recoveries) require SPF calculations to be performed only on the router connected to the region where the link state has changed, reducing the number of routers that must rerun SPF.Fewer messages are advertised between regions, thereby reducing the bandwidth required to send LSAs.