What protocol does the host use to look up the lan address (e.g., 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. Show
Or your computer is unable to display its IP due to various reasons, and you are getting a “No Valid IP Address” error.
In this article, we’ll show you how to find all ip addresses on a network along with device vendors using MAC addresses with different methods for free. Related post: How to Scan network for IP Addresses Understanding ARP
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 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.
Finding IPs with ARPYou 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.
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 that you can download for free. For Windows:Step 1
This will open the command-line interface in Windows. Step 2
Step 3
Step 4.
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
Step 2
Finding IPs with the DHCP Server
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
Step 2
Step 3
Using Sniffers – NmapIf 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
Step 2
Step 3
Finding out the device vendor from a MAC addressOk, 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. Using Wireshark OUI LookupA 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. Using DHCP to view IP infoAlthough 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. Find a Device or IP Address FAQsCan you find an IP address from a MAC address?Yes. Open a Command Prompt window and enter the command arp -a. The output shows all of the IP addresses that are active on your network. The next column in the output is headed Physical Address. This is the MAC address. Look for the line in the output that has the MAC address that you know and note down the IP address on that line. How can I access a device by MAC address?The easiest way to access a device, knowing the MAC address is to use the arp -a command to find the related IP address. With this address, you can access the device using Remote Desktop Management, a Telnet program, or some other connection facility. How can I find a device by IP address? (cmd instructions)You can follow a path to a device if you know its IP address by using the tracert command at the command prompt (cmd). Open a Command Prompt window and type in tracert followed by the IP address that you know. The output will show each router that has a connection to that device will pass through. Which protocol used for finding the MAC address of an IP address?ARP is the protocol used to associate the IP address to a MAC address. When a host wants to send a packet to another host, say IP address 10.5. 5.1, on its local area network (LAN), it first sends out (broadcasts) an ARP packet.
What protocol will a host use to determine the MAC address of a server?If a host wants to locate the MAC address of a target node on the local network, it sends out an ARP request with its IP and MAC address in the SPA (source protocol address) and SHA (source hardware address) fields. The IP address of the target destination node is set in the TPA (target protocol address) parameter.
What is MAC address used for in LAN?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. Some ISPs track their customers by MAC address.
|