Internet, Networking, & Security Home Networking How to Use an IP Address to Find a MAC Address TCP/IP networks track IP addresses and MAC addresses by Bradley Mitchell Writer An MIT graduate who brings years of technical experience to articles on SEO, computers, and wireless networking. our editorial process LinkedIn Bradley Mitchell Updated on April 29, 2020 reviewed by Chris Selph Lifewire Tech Review Board Member Chris Selph is a CompTIA-certified technology and vocational IT teacher. He also serves as network & server administrator and performs computer maintenance and repair for numerous clients. our review board Article reviewed on Apr 24, 2020 Chris Selph Home Networking ISP The Wireless Connection Routers & Firewalls Network Hubs Broadband Ethernet Installing & Upgrading Wi-Fi & Wireless Tweet Share Email 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. There are several reasons you might want to know the MAC address of a remote computer, and it's easy to do by using a command line utility such as Command Prompt in Windows. Alex Dos Diaz / Lifewire 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. However, if the computers are connected to the same TCP/IP network, you can determine the MAC address through a technology called ARP (Address Resolution Protocol), which is included with TCP/IP. 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. How to Use ARP to Find a MAC Address In Windows, Linux, and other operating systems, the command line utility arp 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. 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. ARP is intended to be used by system administrators and is not a typically useful way to track down computers and people on the internet. 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: ping 192.168.86.45 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: Pinging 192.168.86.45 with 32 bytes of data:Reply from 192.168.86.45: bytes=32 time=290ms TTL=128Reply from 192.168.86.45: bytes=32 time=3ms TTL=128Reply from 192.168.86.45: bytes=32 time=176ms TTL=128Reply from 192.168.86.45: bytes=32 time=3ms TTL=128 Use the following arp command to get a list that shows the MAC address of the device you pinged: arp -a The results may look something like this but probably with many other entries: Interface: 192.168.86.38 --- 0x3 Internet Address Physical Address Type 192.168.86.1 70-3a-cb-14-11-7a dynamic 192.168.86.45 98-90-96-B9-9D-61 dynamic 192.168.86.255 ff-ff-ff-ff-ff-ff static 220.127.116.11 01-00-5e-00-00-16 static 18.104.22.168 01-00-5e-00-00-fb static 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.