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How would you communicate with a device when you don’t have the IP?
You might be in a situation where you don’t have the IP address of a device in a local network, but all you have is records of the MAC or hardware address.
Or your computer is unable to display its IP due to various reasons, and you are getting a “No Valid IP Address” error.
Finding the IP from a known MAC address should be the task of a ReverseARP application, the counterpart of ARP.
But RARP is an obsolete protocol with many disadvantages, so it was quickly replaced by other protocols like BOOTP and DHCP, which deal directly with IP addresses.
In this article, we’ll show you how to find IPs and device vendors using MAC addresses with different methods for free.
Understanding ARP
ARP (Address Resolution Protocol) is the protocol in charge of finding MAC addresses with IPs in local network segments.
It operates with frames on the data link layer.
As you might already know, devices in the data link layer depend on MAC addresses for their communication.
Their frames encapsulate packets that contain IP address information.
A device must know the destination MAC address to communicate locally through media types like Ethernet or Wifi, in layer 2 of the OSI model.
Understanding how ARP works can help you find IPs and MAC addresses quickly.
The following message flow diagram can help you understand the concept:
- The local computer sends a ping (ICMP echo request) to a destination IP address (remote computer) within the same segment. Unfortunately, the local computer does not know the MAC address… it only knows the IP address.
- The destination hardware address is unknown, so the ICMP echo request is put on hold. The local computer only knows its source/destination IP and its source MAC addresses. ARP uses two types of messages, ARP Request and Reply.
The local computer sends an ARP REQUEST message to find the owner of the IP address in question.
This message is sent to all devices within the same segment or LAN through a broadcast MAC (FF:FF:FF:FF:FF:FF) as the destination.
- Because the remote computer is part of the same network segment, it receives the broadcast message sent by the local computer. All other computers in the LAN also receive the broadcast but they know that the destination IP is not theirs, so they discard the packet. Only the remote computer with destination IP, responds to the ARP REQUEST with an ARP REPLY, which contains the target MAC address.
- The local computer receives the ARP REPLY with the MAC address. It then resumes the ICMP echo request, and finally, the remote computer responds with an ICMP echo reply.
Finding IPs with ARP
You can use ARP to obtain an IP from a known MAC address.
But first, it is important to update your local ARP table in order to get information from all devices in the network.
Send a ping (ICMP echo reply) to the entire LAN, to get all the MAC entries on the table.
To ping the entire LAN, you can send a broadcast to your network.
Open the Command Prompt in Windows or terminal in macOS and type.
ping 192.168.0.255
My subnet is 192.168.0.0/24 (mask of 255.255.255.0), so the broadcast address is 192.168.0.255 which can be calculated or found with a “Print Route” command in Windows or a “netstat -nr” in macOS. Or can also be obtained with a subnet calculator.
For Windows:
Step 1.
- Open the CMD (Command Prompt)
- Go to the “Start” menu and select “Run” or press (Windows key + R) to open the Run application
- In the “Open” textbox type “cmd” and press “Ok”.
This will open the command-line interface in Windows.
Step 2.
- Enter the “arp” command.
- The arp command without any additional arguments will give you a list of options that you can use.
Step 3.
- Use the arp with additional arguments to find the IP within the same network segment.
- With the command “arp -a” you can see the ARP table and its entries recently populated by your computer with the broadcast ping.
Step 4.
- Reading the output.
- The information displayed in the arp-a is basically the ARP table on your computer.
- It shows a list with IP addresses, their corresponding physical address (or MAC), and the type of allocation (dynamic or static).
Let’s say you have the MAC address 60-30-d4-76-b8-c8 (which is a macOS device) and you want to know the IP.
From the results shown above, you can map the MAC address to the IP address in the same line.
The IP Address is 192.168.0.102 (which is in the same network segment) belongs to 60-30-d4-76-b8-c8.
You can forget about those 224.0.0.x and 239.0.0.x addresses, as they are multicast IPs.
For macOS:
Step 1:
- Open the Terminal App. go to Applications > Utilities > Terminal or Launchpad > Other > Terminal.
Step 2:
- Enter the “arp” command with an “-a” flag.
- Once you enter the command “arp -a” you’ll receive a list with all ARP entries to the ARP Table in your computer.
- The output will show a line with the IP address followed by the MAC address, the interface, and the allocation type (dynamic/static).
Finding IPs with the DHCP Server
The Dynamic Host Configuration Protocol (DHCP) is the network protocol used by TCP/IP to dynamically allocate IP addresses and other characteristics to devices in a network.
The DHCP works with a client/server mode.
The DHCP server is the device in charge of assigning IP addresses in a network, and the client is usually your computer.
For home networks or LANs, the DHCP Server is typically a router or gateway.
If you have access to the DHCP Server, you can view all relationships with IPs, MACs, interfaces, name of the device, and lease time in your LAN.
Step 1.
- Log into the DHCP Server. In this example, the DHCP server is the home gateway.
- If you don’t know the IP address of your DHCP Server/ Gateway, you can run an ipconfig (in Windows) or ifconfig (in macOS/Linux).
- This particular DHCP Server/Gateway has a web interface.
Step 2.
- Enter the IP address on the search bar of the web browser, and input the right credentials.
Step 3.
- Find the DHCP Clients List.
- In this TP-Link router, the DHCP Server functionality comes as an additional feature.
- Go to DHCP > DHCP Clients List. From this list, you can see the mapping between MAC addresses and their assigned IPs.
Using Sniffers
If you couldn’t find the IP in the ARP list or unfortunately don’t have access to the DHCP Server, as a last resort, you can use a sniffer.
Packet sniffers or network analyzers like Nmap (or Zenmap which is the GUI version) are designed for network security.
They can help identify attacks and vulnerabilities in the network.
With Nmap, you can actively scan your entire network and find IPs, ports, protocols, MACs, etc.
If you are trying to find the IP from a known MAC with a sniffer like Nmap, look for the MAC address within the scan results.
How to find the Device and IP with a Sniffer?
Step 1.
- Keep records of your network IP address information.
- In this case, my network IP is 192.168.0.0/24. If you don’t know it, a quick “ipconfig” in Windows cmd or an “ifconfig” in macOS or Linux terminal can show you the local IP and mask.
- If you can’t subnet, go online to a subnet calculator and find your network IP.
Step 2.
- Download and open Nmap.
- Download Nmap from this official link https://nmap.org/download.html and follow its straightforward installation process.
Step 3.
- Open Nmap (or Zenmap) and use the command “sudo nmap -sn (network IP)” to scan the entire network (without port scan).
- The command will list machines that respond to the Ping and will include their MAC address along with the vendor.
- Don’t forget the “sudo” command.
- Without it, you will not see MAC addresses.
Finding out the device vendor from a MAC address
Ok, so now you were able to find out the IP address using “arp -a” command or through the DHCP Server.
But what if you want to know more details about that particular device?
What vendor is it?
Your network segment or LAN might be full of different devices, from computers, firewalls, routers, mobiles, printers, TVs, etc.
And MAC addresses contain key information for knowing more details about each network device.
First, it is essential to understand the format of the MAC address.
Traditional MAC addresses are 48 bits represented in 12-digit hexadecimal numbers (or six octets).
The first half of the six octets represent the Organizational Unique Identifier (OUI) and the other half is the Network Interface Controller (NIC) which is unique for every device in the world.
There is not much we can do about the NIC, other than communicating with it.
But the OUI can give us useful information about the vendor if you didn’t use Nmap, which can also give you the hardware vendor.
A free online OUI lookup tool like Wireshark OUI Lookup can help you with this.
Just enter the MAC address on the OUI search, and the tool will look at the first three octets and correlate with its manufacturing database.
Final Words
Although the RARP (the counterpart of ARP) was specifically designed to find IPs from MAC addresses, it was quickly discontinued because it had many drawbacks.
RARP was quickly replaced by DHCP and BOOTP.
But ARP is still one of the core functions of the IP layer in the TCP/IP protocol stack.
It finds MAC addresses from known IPs, which is most common in today’s communications.
ARP works under the hood to keep a frequently used list of MACs and IPs.
But you can also use it to see the current mappings with the command arp -a.
Aside from ARP, you can also use DHCP to view IP information. DHCP Servers are usually in charge of IP assignments.
If you have access to the DHCP server, go into the DHCP Client list and identify the IP with the MAC address.
Finally, you can use a network sniffer like Nmap, scan your entire network, and find IPs, and MACs.
If you only want to know the vendor, an online OUI lookup like Wireshark can help you find it quickly.
The first step of troubleshooting any network problem is by pinging the IP address. Well, for that you need to know the IP address of the device or in cases IP address of all the devices in the network. There are several ways to do this and it entirely depends on the type of OS you are using. So, here are ways to find the IP Address of other devices in your network whether it is Windows, Android, iOS, Ubuntu and macOS.
Find IP Address of Other Devices on Your Network
In this article, we would be dealing with ways to find the private IP address of devices. Since the public IP address of all the devices within the same network remains the same i.e. the IP address of your router. In case, you are surprised by the word public and private IP address, it’s fairly simple. We have a detailed article on the difference between Public and Private IP and how to find the IP address of your own device.
1. How to Find IP Address in cmd For Network
The simplest way to do that in Windows is via the command line. To open the command prompt, type “cmd” on the Start menu. When you see the command prompt, right click on it and click on “Run as Administrator”.
In case you are using windows 10, you can directly run Command Prompt as an Administrator. Just right-click on the Start icon and click on Command Prompt(Admin).
Once you get the Command Prompt window, type the following command.
This will display the entire list of ARP entries. In case you are wondering, ARP is a network utility which maintains a track of all private IP addresses in the network.
Find IP Address of all Devices on Network Using Windows App
Find IP addresses through the command line might be the simplest way but not the most intuitive one. If you are not good with command line then you should download this Nirsoft utility called Wireless Network Watcher. The app has a portable version as well as exe.
As soon as you open the app, it starts scanning your network. Give it some time and it will list up the active connections in your network. The app will display all computers, smartphones and smart homes devices that are currently connected to the network. Along with the Device Name and IP address, it also presents other relevant information like MAC Address, Device Information etc along with its IP Address.
Read: Useful NirSoft Utilities That Every Windows User Should Try
2. Find all IP Address on the Network on Ubuntu
If you are working with Ubuntu or any Unix based OS then following are the ways. You can find the IP address using arp utility on the terminal. To open the terminal, right-click anywhere on the desktop and select “Open Terminal”.
Alternatively, you can also click on the Activities button at the top-left corner. This will bring up a search bar. Type Terminal on it and click on the Terminal icon once it pops up.
Once the terminal window opens, type the following command.
Another intuitive way to do this is through GUI. You have to install a tool called Angry IP Scanner. To install the Angry IP Scanner, you need to add an entry to the APT repository. APT (Advanced Packaging Tool) will then be able to fetch Angry IP Scanner from that particular location. To add the entry to the repository, type the following command
In case you are facing any issues with IP Scan Installation, make sure you have disabled gpg signatures check. You can do that by using the following command.
Once the entry is successfully added, we need to update the apt-get repository. To do that, type the following command
Once the apt repository is updated successfully, we can install the Angry IP Scanner application. Type the following command to fetch and install the application
Alternatively, if you have a browser you can also choose to install from the Angry IP Scanner website directly. Once you launch the app, it will the network you are connected to. Once, it is completed you can see the active connections in your network.
It has advanced tools like opening an FTP, Telnet, SSH connection for any of the IP devices. One thing it lacks is the inability to show hostnames for the devices. Most of the devices come up as N/A in the hostname. This can, however, be found out by using the host command but that takes an extra step.
Read: How to use Angry IP Scanner – Beginners Guide
3. How to Find who is on my WiFi on macOS
On macOS, the steps are quite similar to that of Ubuntu. To find the IP Address of other devices in your network via the command line, we need to first open the terminal. To do that, hit Cmd + Space to trigger Spotlight Search. Type “Terminal” on the search bar. Click on the Terminal icon when the search results populate.
Once the terminal window opens, type the following command.
This will list down the IP’s in your local network with their MAC Addresses. IPs are listed in round brackets followed by the MAC Address.
You cannot see the hostname (name of the computer or smartphone) through the command line. For that, you will have to do a host search separately for each IP. For example, if I need to find the hostname of 192.168.1.105, then I have to execute the following command
host 192.168.1.105
If the commands sound too much work, you can download a freeware from the Mac App Store called LAN scan. This app will list the IP addresses connected to the Local network along with other details like MAC addresses, Vendor etc. This app does not grab he Hostnames like Wireless Network Watcher. In order to get the hostnames of the devices, you need to get the premium variant. It can be purchased at a one-time fee of $7.
Also Read: Find Out Who’s Connected to Your WiFi
4. Android & iOS
On Android and iOS, there is no native way to check the IP Address of all the devices in the network. Hence, you will have to download a third-party app for this. Fing is a powerful network utility available for both Android and iOS which lets you scan your network. All you have to do is open the app and it will automatically start scanning all of the devices on your network. You’ll see all of their IP addresses, their names.
Unlike all the other apps we tested for Windows and Mac, Fing was the only that can figure out your connected devices brands and models. It can even fetch the device icon – wheater it’s an iPhone, MacBook, Router or Printer etc.
Check out Fing (iOS, Android)
Search For Ip By Mac Address
Apart from just scanning IPs, you can also ping them or see the open ports on the particular device.
5. Router
One of the most popular ways to check who is connected to your WiFi network is by using your router’s web interface.
In case you have access to the router web interface, you can simply log in to the web portal and check. The web portal address, username, and password are mostly printed behind the router. In case you don’t have physical access to the router, the web portal URL is mostly the PC’s gateway address. To find that, open command prompt and type the following command.
The default username and password depends on the router’s manufacturer. Mostly, the username and password is “admin”. In case this doesn’t work for you, visit the official manufacturer site to get the default credentials.
Once you are logged in, look out for the Wireless or DHCP option. We need to navigate to the DHCP client’s list. On this page, you can see the entire list of devices connected to the network with their Client Name and MAC Address. You can also choose to block particular devices from this interface. To read more about it, check our article on how to block someone from your network.
The good thing about this approach is that you don’t have to install any software because you can access your router from any device. However, the only downside is that you need to know the router’s login credentials. If you are in a work environment then you might not have access to these details to log into the routers admin page. In that case, you will have to use the methods mentioned above.
Find Ip From Mac
Final Say
Once you have found the IP address of the devices in your network. You can start configuring your network accordingly. You can start assigning Static IP Addresses to your device, configuring SSH, access your computer remotely etc.