How would you communicate with a device when you don’t have the IP?
- MAC Addresses Can Be Turned Into IP Addresses (Sort Of)
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- Is There Any Way To Find A MAC Address By Using An IP Address?
- Find Ip By Using Mac Address
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.
Type 'arp -a' in the command prompt. This lists a number of MAC addresses with the associated IP addresses. Since you have the MAC address, scroll down the list to find the associated IP address. The MAC address is shown in the 'Physical Address' column with the IP address in the 'Internet Address' column. An example of a table record is in Step 4. How to find your local internal (private/local) IP address. The IP address we discovered using the above method is the external IP address, and that will nearly always be what you need to find out.
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).
MAC Addresses Can Be Turned Into IP Addresses (Sort Of)
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?
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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.
![Find ip for machine Find ip for machine](/uploads/1/3/4/8/134842930/491696926.png)
- 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).
Is There Any Way To Find A MAC Address By Using An IP Address?
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.
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If you are about to start sharing files or setting up a network, you need to know your IP address. As long as you are connected to a network, your device has a unique IP address.
It is also crucial to know your IP address so that you can use it while troubleshooting network connection problems. But how do you find the IP address of your Mac.
Read Article: A Device Attached To The System Is Not Functioning
Don’t worry.
We are going to discuss different solutions. However, before that, let’s find out the meaning of an IP address.
What’s an IP address?
“IP” stands for Internet Protocol Address. This is a numeric address given to all unique instances linked to any device communication network using IP/TCP communication set of rules.
IP addresses are crucial components in networking events that connect the worldwide web. Your Mac can have two IP addresses: the internal IP and the external IP.
Is there any difference between the external IP address and internal IP address?
Related Reading:192.168.1.1 – How To Access Router Admin IP Address
External IP address
An external IP address is a unique address that your internet service provider assigns you. It is also referred to as the public IP address.
Your external IP address shows how other internet users see you. External IP addresses vary depending on the device using the internet.
Even if you are using the same internet service provider, each device will have a unique external IP address, it is dynamic. Your router and Mac will not have the same IP address.
Find Ip By Using Mac Address
Internal IP address
An internal IP address is a unique and private address assigned to your computer. Most of the time, it is your router that assigns your computer a unique address.
There are a limited set of External IP addresses, and that’s why internal IP addresses are used. Internal IP addresses allow you to access a network without using the space of a public IP address.
How can you find the internal IP address on Mac?
There are various ways of finding an IP address on Mac. Let’s have a look at each.
Solution 1: Find your Internal IP Using the Terminal
- You can use the Terminal to find your internal IP.
- Find the utility section on your Application folder.
- Open the Terminal
- Get your IP with the ifconfig command. However, the ifconfig command can give you a lot of unnecessary data. This may be a little confusing.
- Use the ifconfig | grep “inet” | grep -v 127.0.0.1 command to get rid of stuff you don’t need and get your IP address.
- Regardless of the device, you are using; you can use the above command to eliminate the 127.0.0.1 entry.
- You can now copy your IP address which will be displayed near the “inet” entry.
Solution 2: How to find IP address on Mac if you have OS X 10.5
If you have OS X 10.5, here is how you can find your IP address.
- Go to the top left corner of your mac’s screen and click the “Apple” icon
- Choose “System Preferences”
- Click on “Network“
- Choose your main network that is if it’s not on your default. Mostly it’s always there.
- You will see your IP address on the right side below the “status” section.
- Your active connection will be naturally selected by default.
Solution 3: How to find IP address on Mac if you have OS X 10.4
It’s a little different to find your internal IP address on OS X10.4, so use the following steps.
- Find the Apple icon at the corner on the upper left of your screen.
- When you scroll down, you will see system preferences. Select it.
- Click on Network which is on the third row.
- Choose your connection. It’s possible to choose a connection you would like your IP address for from the show dropdown menu.
- Choose AirPort if you have a wireless connection. In case you are using a wired connection, the Built-In Ethernet will work.
- You can now get your IP address by clicking the TCP/IP tab, which will show the address on the settings window.
How can you find your External IP Address on your Mac?
Just like the internal IP, finding the external IP is easy. First of all, if your Mac is part of a network, you can Google “what’s my IP address?” and you will get your public IP address on top of search results.
Below are several other steps you can use and find your external IP address.
1. Use the router configuration page.
- Look for the web interface on settings and access the router.
- Go to the configuration of the page of the router and open it.
- Check the specific IP address from your router documentation. Some of the well-known router addresses include; 192.168.2.1, 192.168.1.1, and 192.168.0.1.
2. Open your router status
Most routers have external IP’s listed in the Wide Area Network Status or the Router Status. You will find your IP listed below the internet Port in the Router Status.
Your IP has four sets of digits, each set having three numbers. Your internet service provider is the one that assigns you your external IP address.
External IP addresses might change from one time to another, and you can use proxies to mask them.
Aside from that, you can also get your external IP address using the following steps:
- Go to Applications followed by Utilities then Terminal
- Copy and paste “curl ipecho.net/plain; echo” in the terminal window.
- Click the “Enter” key of your keyboard
Your external IP address will be displayed in a few minutes after the above steps.
Finding your IP address is crucial because it helps you find other computers with different networks. Through the IP address, it is possible to control remote services using software like Windows Remote Desktop. Besides that, knowing your IP address assists in network troubleshooting. You can troubleshoot a network connection that is failing using Traceroute commands or Ping.