Now that you have all of the pieces of the MX puzzle, let’s put them together and virtualize it. Recall from the very beginning of the chapter that the MX supports multiple Layer 2 networks, which is done via a feature called a routing instance. Each routing instance must have an instance type, and when it comes to virtualizing Layer 2, the instance type will be a virtual switch.
Figure 2-39. Virtual Switch Hierarchy.
In Figure 2-39, VS1 and VS2 represent routing instances with the type of virtual switch, while the default routing instance is referred to as the default-switch routing instance. Notice that each instance is able to have overlapping bridge domains because each routing instance has its own namespace. For example, bridge domain BD1 is present in the default-switch, VS1, and VS2 routing instances, but each bridge domain has its own learning domain per bridge domain.
Perhaps the real question is, what is the use case for virtual switches? This question goes back to the beginning of the chapter to help address scaling and isolation challenges. Perhaps your network provides Ethernet-based services to many different customers. Well, virtual switches are a great tool to segment customers and provide scale, qualified learning, and overlapping bridge domains. Each virtual switch is able to have its own set of IFLs, route tables, bridge domains, and learning domains. ...