How to check if an IP address is free on a network

I'm gonna setup a Wireless router for a customer.
They have subnet 10.253.48.0/24
What can I do to check if the IP 10.253.48.243 is available to set up the router? I'm on out on a local network at my workplace, the customer's network is IPVPN.

I have Access to the Linux console on the out network that can communicate with our customers. I thought that I could use Nmap command to find out if there's any equipment on the network. I tried running the command nmap -sP -PE 10.253.253.0/24 But I dont get the response I'm looking for. What might I do different to find out if this is an available address?

Solution 1:

Ask their network administrator. There is no other way that doesn't risk causing serious problems. It may belong to a machine that's off at the moment.