Like OSPFv2, implementing the multiarea OSPFv3 topology in Figure 1 is simple. There are no special commands required. A router simply becomes an ABR when it has two interfaces in different areas.
For example in Figure 2, R1 is assigned the router ID 1.1.1.1. The example also enables OSPF on the LAN interface in area 1 and the serial interface in area 0. Because R1 has interfaces connected to two different areas, it becomes an ABR.
Use the Syntax Checker in Figure 3 to configure multiarea OSPFv3 on R2 and on R3.
Upon completion of the R2 configuration, notice the message that there is an adjacency with R1 (1.1.1.1).
Upon completion of the R3 configuration, notice the message that there is an adjacency with R2 (2.2.2.2).