How can I install an IP scanner for Ubuntu 16.04 LTS?

Question

I simply need a way to install a subnet IP scanner so I can see which devices are connected.

In searching around I have found a lot of old web pages that talk about changing repositories to get angry IP scanner, but I do not want to change my repositories for any reason. Plus, these pages all are for older versions.

There is an arp command but it is not exhaustive. arp -a does not show the entire subnet; just connections from a single machine.

I never did find a clone of Advanced IP scanner.

So the question is in the title: How can I install an IP scanner for Ubuntu 16.04 LTS?

Solution

Here are two that work reasonably well with Ubuntu 16.04 LTS.

The first one, arp-scan, accomplished the primary goal of ennumerating devices. The second one, nmap, is much more versatile and gives a quick picture of the services available from each device.

1) arp-scan

Installation is easy:

sudo apt-get update
sudo apt-get install arp-scan

It has a ton of options, which can be seen here:

sudo arp-scan --help

For basic enumeration, to scan my "local" net, is:

sudo arp-scan -l | sort

Which results in a very basic display which shows each device including IP address, MAC address and manufacturer of the interface. It also showed "dup" responses for some of the addresses.

2) nmap

sudo apt-get update
sudo apt-get install nmap

To run a Fast scan, which lists devices and shows open ports

nmap -F 192.168.8.1-254

The result is a fairly complete list of devices and open ports.

Here is a handy NMAP Cheat Sheet to see some of the ways to use nmap.

---

I am surprised neither is installed by default in Ubuntu 16.04, but it is quick and easy to make both of them work.

Comments

[SDsolar]

Note the warnings below. But they are great tools.

[derHugo]

Anyway be careful with both! Scanning (accidentally or not) outside of your local/private network is assumed to be a network attack and will be punished.

[SDsolar]

So noted, @derHugo. Thank you for the reminder. This is a good warning to have on the database. ----> Folks, get what he is saying here: Walking down the street checking people's front doors to see if they are locked or looking to see if their windows are open can be considered a hostile act. <------

[SDsolar]

And for those who are curious, YES, Google has a waiver. At this point it would probably not be legal to set up your own web crawler. Trust me that you don't have the resources to fight a test case. And there are some in progress already. Here is an interesting analysis on the subject: benbernardblog.com/…

[SDsolar]

On the upside, nmap showed me that I had a few issues to deal with. Ports that shouldn't have been open, like 21, 80, 8080. I used the tools lsof -i tcp:80 and netstat -plunt to figure out what was causing them and was able to reduce my internal open ports to two I use: 22 for ssh and one other for RDP. No SMB here at all. Great tool. Mind you, I am behind a physical name-brand firewall with just two rules, and two layers of routers here. This subnet is critical to the solar power station. Good practice means at least 3 layers all of different brands, with one being a real firewall.