ipdetect

Detect a new IP address used on a subnet.

When building an IoT device, you can't connect to it using SSH until you know the IP address. This is a simple utility that I created as a wrapper around an nmap ARP scan to find and report the IP address of a new device on the network.

I created this script to make it easy to find the IP address of a new headless computer, like a Raspberry Pi, or an IoT device on the network. This is a tool I developed for my own necessity, feel free to use it as you wish. The underlying mechanism is an ARP scan, with a few extra features to make it more convenient.

Note: Only tested on Linux.

Requirements

Python 3
python-libnmap module

Install

Get this repository

$ git clone https://github.com/jsprada/ipdetect

Change into the directory

$ cd ipdetect

Install the required Python modules

$ sudo pip install -r requirements.txt

Make the script executable (optional)

$ chmod +x ipdetect

Run it

$ ./ipdetect

or (if you opt out of making it executable):

$ pyhton ipdetect

Setup

Edit ipdetect file. There are two variables near the beginning of the script, ip_range and ignore_list

ip_range

The subnet that you wish to scan.
For example, to scan a 192.168.1.x subnet, use 192.168.1.0/24 to scan a 10.0.0.x subnet, use 10.0.0.0/24

ignore_list

A list of IP addresses to ignore. This is useful if you have a previously known wifi device, like a phone, printer, tablet, laptop, etc. that bobs on and off the network. Add those addresses to this list, and ipdetect will ignore it.

Use

Run the script from a computer on the network, it will start scanning. First it will inventory the existing devices on the network and store these as a baseline scan. Connect and start up your Pi or IoT device on the network. When found, the new address will be displayed and the script will stop. Press CTRL-C to stop the script manually.

Example output:

$ ./ipdetect
Starting scan on: 192.168.1.0/24. Press CTRL-C to stop
Ignoring ['192.168.1.140', '192.168.1.138']
Establishing baseline scan
 - 192.168.1.1 is up
 - 192.168.1.2 is up
 - 192.168.1.16 is up
 - 192.168.1.22 is up
 - 192.168.1.100 is up
 - 192.168.1.104 is up
 - 192.168.1.108 is up
 - 192.168.1.110 is up
 - 192.168.1.198 is up
Connect your new device now.
Scanning for new IPs
 - 192.168.1.1 is up
 - 192.168.1.2 is up
 - 192.168.1.16 is up
 - 192.168.1.22 is up
 - 192.168.1.100 is up
 - 192.168.1.104 is up
 - 192.168.1.110 is up
 - 192.168.1.140 is up
 - 192.168.1.198 is up
Ignoring ['192.168.1.140']
No new IPs detected yet
Scanning for new IPs
 - 192.168.1.1 is up
 - 192.168.1.2 is up
 - 192.168.1.16 is up
 - 192.168.1.22 is up
 - 192.168.1.100 is up
 - 192.168.1.104 is up
 - 192.168.1.105 is up
 - 192.168.1.108 is up
 - 192.168.1.110 is up
 - 192.168.1.140 is up
 - 192.168.1.198 is up
Scan stopped, new IP detected: ['192.168.1.105']

Todo

objectify/cleanup/reorganize/
auto-detect IP range
compile and add to AUR for Arch Linux users.