nmap Command Examples in Linux

The nmap (network mapper) is a network mapping tool widely used by sysadmins, Network engineers, and even hackers for host discovery.

Apart from host discovery, it can also be used to discover rules on ports, OS detection, vulnerability scanning (hello hackers), and more.

So in this guide, I will show you practical examples of the nmap command.

Practical examples of the nmap command

While you would find the nmap package pre-installed on most of the Linux distros, you might not have it pre-installed.

To know whether you have it installed or not, verify the installed version:

nmap -v

And if it shows an error, you can refer to the given command.

To install nmap on Ubuntu/Debian base:

sudo apt install nmap

For RHEL/Fedora base:

sudo dnf install nmap

For Arch-based distros:

sudo pacman -S nmap

Now, let's jump to the examples.

1. Scan for open ports on the network

To search for open ports, all you have to do is append the domain name or the IP address to the nmap command:

nmap Target

But if you are in hurry and want to finish the scan as soon as possible, you can use the -F flag:

nmap -F target

2. Scan multiple hosts

You may have to scan multiple hosts and nmap offers various ways to scan multiple hosts at the same time for an extensive search.

So there are several ways to scan multiple hosts:

• Appending multiple domains or IP addresses to the nmap command
• Using wildcards to search the entire subnet at once
• By specifying a range of IP address
• You can also append the different endings of IP addresses rather than typing the entire IP.

So let's start with appending the multiple domains/IP addresses.

Scan multiple hosts by appending domains or IP addresses

So basically, if you have to scan 2-3 hosts, this is the easiest method in my opinion where you simply append the IP/domain one by one.

For example, here, I have scanned 3 IP addresses at once:

nmap 192.168.1.9 192.168.1.8 192.168.1.10

Use a wildcard to scan the entire subnet

If you have to scan multiple hosts and the list is long enough to make you tired while typing, you can use the wildcard.

To use the * wildcard, type the IP address, and replace your last octet (the last part of your IP after the . )with the * symbol:

nmap 192.168.1.*

Scan multiple hosts by specifying the IP range

So let's say I want to scan 3 IP addresses. Now, typing each one manually is not the way I and most of you would prefer.

And in that case, you can specify the range of IP addresses.

For example, here, I scanned for IP addresses from 192.168.1.8 to 192.168.1.10:

nmap 192.168.1.8-10

Scan multiple hosts by appending the ending octet

You can scan multiple hosts by appending the last part of your IP address.

For example, here, I have searched for: 192.168.1.8, 192.168.1.9, and 192.168.1.10 by appending the last octet:

nmap 192.168.1.8,9,10

3. Exclude the host while scanning

When you scan multiple hosts, it is not necessary you'd always want to scan each one from the given range.

And in that case, you use the --exclude flag and append the host which needs to be ignored while performing the scan.

For example, here, I want to ignore 192.168.1.6 while scanning the subnet so I will be using the following:

nmap 192.168.1.* --exclude 192.168.1.6

4. Perform a scan to detect filtering on the Firewall

You can use the nmap command to send ACK packets and it will check whether the target system has a firewall enabled if yes, it will list unfiltered ports.

For this purpose, you will have to use the -sA flag with superuser privileges:

sudo nmap -sA Target

5. Get information about the services of hosts

Once you know about services after scanning ports, you may want to know more about those services.

So in that case you can use the sV flag:

nmap -sV Target

5. Scan for specific ports

To specify a port, to search, you will have to use the -p flag:

nmap -p port_no Target

So let's say I want to perform a scan over port no 443, then I will be using the following command:

nmap -p 443 scanme.nmap.org

Similarly, you can append multiple port numbers if you want to scan multiple ports:

nmap -p 443,80 scanme.nmap.org

Or, you can also specify the range of ports if you want to perform extensive port scans:

nmap -p 20-80 scanme.nmap.org

6. Perform scan in stealth mode

Stealth scans are performed when you want to bypass the firewall as these scans make the target system respond without establishing the full connection.

A yet another reason why hackers love this utility!

To perform a stealth scan, all you have to do is use -sS a flag with superuser privileges:

sudo nmap -sS Target

7. Get OS information of the host

As I mentioned in the beginning, the nmap command can also be used to find the OS information of the targeted host.

To get the OS info, all you have to do is use the -A flag while scanning:

nmap -A Target

8. Identify the host

Not a huge feature but can be helpful when dealing with multiple machines at the same time.

You can append the -sL flag to the nmap command and it will get you the hostname without any additional information about the target:

nmap -sL Target

Similarly, you can use the wildcard * with the IP and it will get the hostname of every system inside the subnet:

nmap -sL 192.168.1.*

9. Find active hosts

Generally, we use the ping command to check whether the host is up or not and the nmap command can also be used to ping hosts.

To ping hosts, you will have to use the -sP flag:

nmap -sP 192.168.1.0/24

10. Scan the network faster with nmap time policies

The nmap allows you to choose from 5-time policies ranging from T0 to T5. Where the T0 is the slowest and the T5 is the fastest.

The nmap utility operates on T3 by default, so you can tweak the speeds as per your needs.

To use the time policy, follow the given command syntax:

nmap [Time_Policy] Target

For example, here, I went with the T4 to achieve better speeds than the defaults:

nmap -T4 scanme.nmap.org

11. Find host interfaces and routes

To find the host interfaces and routes, all you have to do is execute the nmap command with the --iflist flag:

nmap --iflist

A pretty neat way of getting host interfaces and routes. Isn't it?

Seek more like nmap? We got you!

If you want to know more networking commands, we have covered 21 networking commands with their examples:

21 Basic Linux Networking Commands You Should Know

A list of basic Linux networking commands that will help you troubleshoot network issues, monitor packets, connect devices, and much more.

It's FOSSSagar Sharma

I hope you will find this guide helpful.

And if you want me to cover something else, or have any queries related to this guide, let me know in the comments.