A large network scale leads to a huge LSDB size, causes
routers to consume much storage space, affects network performance.
To prevent these problems, you can configure OSPFv3 to divide an AS
to different areas
In certain cases, the direct physical connection between a backbone area and a non-backbone area can hardly be realized. Thus, you can configure virtual links for the ABR that is not directly connected to the backbone area. Virtual links are mainly used for redundancy backups. The other ends of virtual links also need corresponding configurations.