Virtual system (VS) applications are as follows:
Different routing instances are isolated, which is more secure and reliable than route isolation implemented using VPN.
Physical resources of a device can be fully utilized. For example, without the VS technique, on a device with 16 interfaces, if only 4 interfaces are needed to transmit services, the other 12 interfaces idle, wasting resources.
Devices of different roles are integrated to simplify network tests, deployment, management, and maintenance.
Links between devices are simplified into internal buses that are of higher reliability, higher performance, and lower cost.