- What Are Mac Addresses Used For People
- What Are Mac Addresses Used For Business
- What Are Mac Addresses Used For Iphone
- Mac Addresses Lookup
- List Mac Addresses On Network
The MAC address is an important element of computer networking. MAC addresses uniquely identify a computer on the LAN. MAC is an essential component required for network protocols like TCP/IP to function. Computer operating systems and broadband routers support viewing and sometimes changing MAC addresses. MAC Address is used to identify the node within the network. IP Address is used to identify the node in any network. Port address used to identify the process within the node. If you need more clarifications.
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.
What Are Mac Addresses Used For People
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.
What Are Mac Addresses Used For Business
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.
This tutorial explains the MAC (Media Access Control) address in detail. Learn what the MAC address is, how it is formed, and the types of MAC addresses (unicast, multicast, and broadcast).
In network, an address provides a unique identity to an end device. Unless an end device has a unique address, it can’t communicate with other devices in the network. A unique address enables an end device to send and receive data in the network.
In the LAN network, a unique address is the combination of two addresses; software address and hardware address.
Addressing in Networking Reference models
A networking reference model defines the standards, characteristics, definitions, and functionalities of the network. There are two popular networking models; the OSI Seven Layers model and the TCP/IP model.
In both models, the software address and hardware address are defined in the network layer and data link layer, respectively. In both models, the network layer and data link layer stand on the third and second positions, respectively. Because of this, both layers are also known as layer 3 and layer 2, respectively.
Software address
The software address is also known as the network layer address or layer 3 address. This address is manageable and configurable. Based on network requirements and layout, this address can be configured and assigned to an end device. Almost all modern LAN implementations use the IP protocol in the network layer. The IP protocol uses the term IP address to define the software address.
I have already explained IP addresses in the following tutorial.
In this tutorial, I will explain the hardware addresses in detail.
Hardware address
The hardware address is also known as the data link layer address or layer 2 address or MAC (Media Access Control) address. From these terms, the term MAC address is commonly used to refer to the hardware address. Unlike the IP address or software address, this address can’t be configured or managed. When you purchase a new NIC (Network Interface Card), or any device which has onboard NICs, it comes with a pre-configured MAC address.
What Are Mac Addresses Used For Iphone
A MAC address is 6 bytes (48 bits) long address in the binary numbers. MAC addresses are written in the hexadecimal format. The hexadecimal format uses the base-16 to refer to numbers. If we divide the total available length (48 bits) in binary numbers by the base (base-16) that is used to write a number in hexadecimal format, we get the total digits (12 = 48 ÷ 16) of that number in the hexadecimal format. Thus, if we write a 6 bytes (48bits) long binary MAC address in hexadecimal format, we get a 12 digits long hexadecimal number.
For convenience and easier readability, when writing a MAC address in hexadecimal format, extra space or periods or colons are added after every two or four digits. For example, you can write a MAC address in the following ways.
- Without any separator: - 00000ABB28FC
- Extra space after every two digits: - 00 00 0A BB 28 FC
- Extra space after every four digits: - 0000 0ABB 28FC
- Colon after every two digits: - 00:00:0A:BB:28:FC
- Colon after every four digits: - 0000:0ABB:28FC
- Period after every two digits: - 00.00.0A.BB.28.FC
- Period after every four digits: - 0000.0ABB.28FC
No matter which style you use to write the MAC address, or an application or networking software uses to display the MAC address, a MAC address is always processed in binary numbers only. NIC converts hexadecimal numbers of the MAC address in binary numbers before processing and using it.
Structure or format of the MAC address
As mentioned above, you can’t assign MAC address to a NIC or onboard NICs. When you purchase a new NIC or a device with onboard NICs, it arrives with a pre-configured MAC address or MAC addresses, respectively. Before we understand how manufacturers select MAC addresses for NICs, let’s briefly understand why a MAC should be unique in the LAN network.
If a LAN network has two or more NICs configured with the same MAC address then that network will not work. Let’s understand this with an example.
Suppose in a network three PCs; PC-A (11000ABB28FC), PC-B (00000ABB28FC) and PC-C (00000ABB28FC) are connected through a switch. NICs of PC-B and PC-C have the same MAC address 00000ABB28FC.
If PC-A sends a frame to the destination MAC address 00000ABB28FC, the switch fails to deliver this frame as it has two recipients of this frame.
The following image shows this example.
A LAN network does not work unless each device in the LAN network has a unique MAC address.
Now let's be back to our main question. How do manufacturers assign a unique MAC address to each NIC?
Before manufacturing NICs, every manufacturer obtains a universally unique 3-byte code, known as the organizationally unique identifier (OUI), from the IEEE. The IEEE is an international organization that regulates and maintains the namespace of MAC addresses.
After obtaining the OUI bytes, the manufacturer uses these OUI bytes at the beginning of the MAC address of all its NICs or on-board NIC devices. The manufacturer also assigns a unique hexadecimal value in the remaining bytes.
6 bytes MAC address = 3 bytes OUI number obtained from the IEEE + 3 bytes unique number assigned by the manufacturer
MAC addresses of all NICs or onboard NIC devices manufactured by the same manufacturer always start with the same 3-bytes OUI numbers. For example, suppose the IEEE assigns an OUI “0000AA” to the xyz company. Now the xyz company will use the OUI number 0000AA as the first 24 bits to build MAC addresses for its NICs or onboard NICs devices.
To keep each product separately from others, the manufacturer uses the remaining 3-bytes. Manufacturers are free to use any sequence or method on the remaining three bytes. For example, the xyz company can assign the MAC addresses to its NICs in the incremental order.
The following table extends this example and adds two more demo companies (ABC and JKL) in the example. It also shows MAC addresses of 5 NICs from each company.
Thus, this procedure ensures that no two NICs use the same MAC address in the universe.
Types of MAC address
There are three types of MAC address; unicast, multicast, and broadcast.
Unicast MAC address
Unicast MAC address represents a specific NIC or onboard NIC ports in the network. The inbuilt MAC address of a NIC is the unicast MAC address of that NIC.
Multicast MAC address
Multicast MAC address represents a group of devices (or NICs in Layer 2). The IEEE has reserved the OUI 01-00-5E (first 3-bytes or 24 bits) for the multicast MAC addresses. The remaining 24 bits are set by the network application or device that wants to send data in the group. A multicast MAC address always starts with the prefix 01-00-5E.
Broadcast MAC address
Mac Addresses Lookup
Broadcast MAC address represents all devices in the network. The IEEE has reserved the address FFFF.FFFF.FFFF as the broadcast MAC address. Any device that wants to send the data to all devices of the network, can use this address as the destination MAC address.
List Mac Addresses On Network
That’s all for this tutorial. If you like this tutorial, please don’t forget to share it with friends through your favorite social channel.