D-Link DGS-3612G Product Manual - Page 230

xStack® DGS-3600 Series Layer 3 Managed Gigabit Ethernet Switch Figure 4- 50. NSSA Area example The NSSA ASBR (Not So Stubby Area Autonomous System Border Router) is receiving External Route information and translating it as an LSA Type-7 packet that will be distributed ONLY to switches within the NSSA (Area 2 in the example above). For this route's information to enter another area, the LSA Type-7 packet has to be translated into an LSA Type-5 packet by the NSSA ABR (Area Border Router) and then is distributed to other switches within the other OSPF areas (Area 1 and 2 in the example above). Once completed, new routes are learned and new shortest routes will be determined. To alleviate any problems with OSPF summary routing due to new routes and packets, all NSSA area border routers (ABR) must support optional importing of LSA type-3 summary packets into the NSSA. Type-7 LSA Packets Type-7 LSA (Link State Advertisement) packets are used to import external routes into the NSSA. These packets can originate from NSSA ASBRs or NSSA ABRs and are defined by setting the P-Bit in the LSA type-7 packet header. Each destination network learned from external routes is converted into Type-7 LSA packets. These packets are specific for NSSA switches and the route information contained in these packets cannot leave the area unless translated into Type-5 LSA packets by Area Border Routers. See the following table for a better description of the LSA type-7 packet seen here. Figure 4- 51. LSA Type-7 Packet 214