Unified ISSU: Virtual Chassis support

You can perform a unified in-service software upgrade (unified ISSU) on member routers in an MX Series Virtual Chassis configuration. Unified ISSU enables you to upgrade the system software on the Virtual Chassis member routers with minimal traffic disruption and no disruption on the control plane. To start a unified ISSU in an MX Series Virtual Chassis, issue the request system software in-service-upgrade package-name command from the primary Routing Engine in the Virtual Chassis primary router (VC-Pp). This command always reboots each of the four Routing Engines in the Virtual Chassis.