I'm gonna setup a Wireless router for a customer.
They have subnet
What can I do to check if the IP 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 But I dont get the response I'm looking for. What might I do different to find out if this is an available address?

  • As a side note.. I've noticed that whenever I do scans of an entire subnet, I never get good results unless I set the --scan-delay option. I scanned a network here just now using your nmap string which returned 54 hosts. Adding the scan-delay, It brought back 74 hosts, which is closer to what I was expecting.
    – Safado
    Feb 25, 2013 at 15:29
  • Can you just ping the ip address to see if there's a response? If there's no response its free? Jul 3, 2014 at 5:16
  • As a sidenote, use nmap as root. It happens a lot of times that ping is working and nmap is not for this reason. Nov 23, 2020 at 17:47

1 Answer 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.

  • 14
    Many people have decided that they are too clever for this answer, and even more people have been woken up in the middle of the night as a consequence. Thousands of dollars in labor are lost every year to ignoring this.
    – Andrew B
    Feb 4, 2013 at 9:21
  • 1
    +1. If the customers does not have an allocation plan, he deserves what he gets - namely a clueless contractor setting up a bad ip.
    – TomTom
    Feb 25, 2013 at 15:58

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