You need to assign an IP to the management interface so you can access the router via SSH.
The chassis requires three fan tray slots, which house N+1 hot-swappable fans. Nokia Documentation Center 2. Hardware Installation Steps Chassis Mounting: nokia 7250 ixr x1 installation guide
: Secure the rack-mount brackets to the chassis. Install the router into the rack and tighten the screws. You need to assign an IP to the