EX8200 Virtual Chassis Overview
An EX8200 Virtual Chassis is multiple Juniper Networks EX8200 Ethernet Switches connected together that operate as a single network entity. The advantages of connecting multiple EX8200 switches into a Virtual Chassis include better-managed bandwidth at a network layer, simplified configuration and maintenance because multiple devices can be managed as a single device, and a simplified Layer 2 network topology that minimizes or eliminates the need for loop prevention protocols such as Spanning Tree Protocol (STP).
The XRE200 Routing Engine is the device that connects all member switches into a single Virtual Chassis. An EX8200 Virtual Chassis is formed by connecting a Virtual Chassis port (VCP) on an XRE200 External Routing Engine to the management ports (labeled MGMT) on the internal Routing Engines of the EX8200 member switches. A member switch is any switch that is part of a Virtual Chassis.
You can add a second XRE200 External Routing Engine to an EX8200 Virtual Chassis topology to provide external Routing Engine redundancy. See Understanding EX8200 Virtual Chassis Topologies.