9tut ccna wireless 200-355

9tut ccna wireless 200-355.Figure 8-6 Single-area OSPFIn larger OSPFv2 networks, using a single-area design can cause some problems. For example, imagine an enterprise network with 900 routers (instead of just 11), and several thousand subnets. It turns out that the CPU time required to run the SPF algorithm on all the topology data is very long. As a result, the OSPFv2 convergence time (the time it takes to react to changes in the network) may be slow. The router's RAM may also be insufficient. Other issues are the following.. Larger topology databases require more memory on each router.Processing larger topology databases with SPF algorithms requires exponentially more processing power as the topology database grows larger.A change in the state of an interface anywhere in the interconnected network (from up to down, or down to up) forces each router to run SPFI againThe solution is to use OSPF regions, which split a large LSDB into several smaller LSDBs. using regions, each link is placed into a region. the SPF performs its complex mathematical operations on the topology within a region, and these operations are limited to the topology of that region. For example, an interconnected network with 1000 routers and 2000 subnets is split into 100 regions, each with an average of 10 routers and 20 subnets. The SPF calculation on a router will only handle a topology of about 10 routers and 20 links, not 1000 routers and 2000 links.So how big can a network be before OSPF needs to use regions? There is no fixed answer, because the behavior of SPF processing depends heavily on the processing speed of the CPU, the amount of RAM, the size of the LSDB, and so on. In general, networks with more than a few dozen routers can benefit from zones, and over the years, some documents have listed 50 routers as the cutoff for when a network should really use zones.The next few pages explore how OSPF zone design works and why zones can help larger OSPF networks work more3.2 Foundational Content 167well for more reasons. OSPF Regions