Juniper MX Series

What is Virtual Chassis?

Virtual chassis is very similar to a distributing computing concept called a single system image (SSI), which is a cluster of devices that appears to be a single device. However, simply appearing to be a single device isn’t good enough; all of the fault tolerance features that are available in a physical chassis need to be present in the virtual chassis as well. This creates a unique engineering challenge of constructing a virtual chassis that looks, feels, and behaves like a true chassis, as shown in Figure 6-1. The two routers R1 and R2 are joined together by a virtual chassis port (VCP) to form a virtual chassis.

Figure 6-1. Illustration of Virtual Chassis.

Once the two routers have been configured to participate in virtual chassis, the virtual chassis will now act as a single router. For example, when you log in to the router and execute commands such as show chassis hardware or show interfaces terse, you will see the hardware inventory and interface list of both routers.

There are several features that contribute to the high availability in a typical chassis:

• Redundant power supplies

• Dual routing engines

• Nonstop routing

• Nonstop bridging

• Graceful routing engine switchover

• Multiple line cards

Each component is fully redundant so that there isn’t a single point of failure within a single chassis. Virtual chassis takes the same high-availability features that are found ...