Find IP address by MAC address

Sometimes it is needed to determine IP address of a network device or a PC but only MAC address is known.

This is mostly problem for network devices like network printers or IP CCTV cameras. For example we connected such a device to a network with DHCP and we’d like to know what IP address the device got from DHCP server. May be a device has a static IP address configured but we can’t remember it while MAC address is known (labeled on the box). Same question may be for remote computers.

A simple way to find IP address works on any PC and requires no administrative permissions – find IP address from ARP cache list by filtering the list by known MAC address:

This is simple but the record for a particular address may not present in the list.

The main reason for that is Windows keeps ARP cache records for 15-45 seconds, see Address Resolution Protocol (ARP) caching behavior in Windows Vista TCP/IP implementations for more details. That means a record related to the particular MAC address could be deleted and therefore unavailable.

To get full list of ARP records one can use standard ping utility. The simplest way is to ping all possible IP addresses in the LAN. For a network like 192.168.1.1 / 255.255.255.0 the command would be like that:

Important that ping utility processes would be started with do @start /b ping because:

• all ping processes will start at the same time (not waiting for another ping finishes) so it will take only several seconds. If type just do ping without start the loop will take about 10 minutes.
• @ characters before start hides output from 254 ping processes

Then run arp -a immediately after loop finishes. Waiting for 15 seconds or more can result in some ARP records will be dropped.

Below is a batch file ip_by_mac.cmd to perform these actions. MAC address to search expected in command line argument:

Please note for statement uses double percentage sign – that’s correct for batch files.

Starting the batch file:

The file is small and simple in use but can be used in networks 255.255.255.0.

The video shows how to find IP address in 192.168.0.x network for known 00-0C-29-01-7C-3F MAC address from command line window:

The video shows three steps.

Firstly checking ARP cache if it already contains a record for MAC 00-0C-29-01-7C-3F:

The empty output means there’s no records for MAC 00-0C-29-01-7C-3F in ARP cache.

Next polling all 254 addresses in FOR /L loop:

The output is again empty, that’s OK.

Finally checking ARP cache again:

This time the output is not empty telling correct IP address:

See also

The batch file to find IP address can be downloaded by this link

How to Use an IP Address to Find a MAC Address

TCP/IP networks track IP addresses and MAC addresses

What to Know

• Ping the device you want to find a MAC address for using the local network address. Then, enter the ARP command.
• Look for the IP address in the results. The Mac address is next to the IP address.

This article explains how to find a MAC address using an IP address by using the command line utility ARP. Additional information is provided about checking your router’s connection data for an IP address.

How to Use ARP to Find a MAC Address

In Windows, Linux, and other operating systems, the command line utility ARP (Address Resolution Protocol) shows local MAC address information stored in the ARP cache. However, it only works within the small group of computers on a local area network (LAN), not across the internet.

ARP is intended to be used by system administrators, and it is not typically a useful way to track down computers and people on the internet.

TCP/IP computer networks use both the IP addresses and MAC addresses of connected client devices. While the IP address changes over time, the MAC address of a network adapter always stays the same.

Using ARP, each local network interface tracks both the IP address and MAC address for each device it has recently communicated with. Most computers let you see this list of addresses that ARP has collected.

Here is one example of how to find a MAC address using an IP address.

Start by pinging the device you want the MAC to address for:

Use a local address, so if your network is 10.0.1.x, then use that number to ping. The ping command establishes a connection with the other device on the network and should show a result like this:

Use the following ARP command to get a list that shows the MAC address of the device you pinged:

The results may look something like this but probably with many other entries:

Find the device’s IP address in the list. The MAC address is shown right next to it. In this example, the IP address is 192.168.86.45, and its MAC address is 98-90-96-B9-9D-61.

Check Your Router’s Connection Data

To find the MAC address of the device connected to your router—assuming you can access the router’s administrative control panel—log in and check for connected devices. Each active device, as well as recently connected devices, should list the local IP address as well as the MAC address.

There’s another method used to find the MAC address of the computer you’re currently using, which involves using the ipconfig /all command in Windows.

Why Figure Out a MAC Address?

A single device can possess multiple network interfaces and MAC addresses. A laptop computer with Ethernet, Wi-Fi, and Bluetooth connections, for example, has two or sometimes three MAC addresses associated with it, one for each physical network device.

Reasons to track down the MAC address of a network device include:

• To set up MAC address filtering on a router to restrict local network access to only those devices whose addresses match a list of presets.
• To determine the device’s manufacturer (first half of the address) and serial number (second half of the address) for service. It’s important to note that the second half of the address is not always the serial number, so it might not work for warranty requests.
• To masquerade (spoof) the identity of a different device. MAC addressing spoofing can be used legitimately to register a home network gateway device with an internet provider. It can also have malicious intent, such as to defeat the MAC address filtering feature to break into the network.

Limitations of MAC Address Lookups

It isn’t usually possible to look up MAC addresses for devices that are outside a person’s physical reach. It often isn’t possible to determine the MAC address of a computer from its IP address alone because these two addresses originate from different sources.

A computer’s hardware configuration determines its MAC address, while the configuration of the network it is connected to determines its IP address.

Find Device or IP Address using Mac Address Free – Here’s a Quick Tutorial & Guide!

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:

1. 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.
2. 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.

1. 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.
2. 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.

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 that you can download for free.

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, Download this Free Subnet Calculator tool or 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.