Connect to a network device without knowing its IP address

A handy tip from Linux Format (LXF147).  If you have an appliance which is turned on but you do not know its IP address you can still connect over the network using the arp table.

On pretty much any appliance there will be a sticker with model number, version etc.  Most appliances will also show their mac address on these stickers and you can use this to connect over the network.
To show the current arp table which might already contain the device run

sudo arp -n

If its not shown then you can assign a temporary IP address for use from your computer with:

sudo arp -s <IP ADdress> <MAC address>

This is a lot quicker than starting something like nmap and scanning whole network ranges to try and spot the IP address you need.  With this you should be able to connect to that new network storage device you just plugged in and browse its admin interface to discover and/or set its propper IP address.