Thank you for taking the time to reply.
I have a laptop and a VOIP phone connected to a Mikrotik Router and I wish to log in to the phones GUI from the laptop but cant find the phones address.
I have Linux installed on the laptop.
Well how is the VoIP phone getting its address? Via dhcp? If so, asking the dhcp server for the current leases is a hint, but just because there is a valid lease doesn't necessarily mean the device is online (powered on).
here are some hints
/ip address print
/tool ip-scan address-range=<network/mask> interface=<interface>
/ip arp print
/ip dhcp-server lease print