 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 con- verge faster. The DR calculates the best paths, then propagates that information to its neighbors 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 involves the router interface's OSPF priority. The default priority is 1, which the lowest value an interface can have, and still be elected the DR. A value of 0 indicates that the router is ineligible to become the DR on the network. Setting the priority higher increases the chances that the router will be elected the DR. The OSPF interface priority is configured using the interface command ip ospf priority. The valid range is 0-255. Ideally, you should plan which router is to become the DR, and set its priority accordingly. Usually, there is an obvious choice, such as a hub or core router, or per- haps just the most powerful router on the network. The designated router will be doing more work than the other routers, SO it should be the one with the most horse- power. If your design includes a hub router, that router will need to be the DR because it will be the center of the topology. If the OSPF interface priority is not set, resulting in a tie, the router will use the OSPF router ID to break the tie. Every router has an OSPF router ID. This ID can be con- figured manually with the router-id command. If the router ID is 