erted to type-5 LSAs by NSSA ASRs for advertisement into the backbone. OSPF separates networks into areas. The core area, which all other areas must connect with, is area zero. One of OSPF's perceived benefits is that it forces you to design your network in such a way that there is a core with satellite areas. You can certainly build an OSPF network with only an area zero, but such a design usually doesn't scale well. There are two main types of areas: backbone and nonbackbone. Area zero is the back- bone area; all other areas are nonbackbone areas. Nonbackbone areas are further divi- ded into the following types: Normal area An OSPF area that is not area zero and is not configured as one of the other types. No special configuration is required. Stub area An OSPF area that does not allow ASE LSAs. When an area is configured as a stub, no O E1 or O E2 routes will be seen in the area. Totally stubby area (TSA) An OSPF area that does not allow type-3, -4, or -5 LSAs, except for the default summary route. TSAs see only a default route and routes local to the areas themselves. Not SO stubby area (NSSA) No type-5 LSAs are allowed in an NSSA. Type-7 LSAs that convert to type 5 at the ABR are allowed. NSSA totally stub area NSSA totally stub areas are a combination of totally stubby and not SO stubby areas. This area type does not allow type-3, -4, or -5 LSAs, except for the default summary route; it does allow type-7 LSAs that convert to type 5 at the ABR. On Ethernet and other broadcast networks, OSPF elects a router to become the des- ignated router and another to be the backup designated router. Calculating OSPF routes can be CPU-intensive, especially in a dynamic network. Having one router that does the brunt of the work makes the network more stable and allows it to converge faster. The DR calculates the best paths, then propagates that information to its neigh- bors within the network that are in the same area and OSPF process. OSPF dynamically elects the DR through a relatively complicated process. The first step