This article explains how to find a MAC address with an IP address using the ARP command line utility. It also contains additional information on checking your router's connection information for an IP address.

In Windows, Linux, and other operating systems, the Address Resolution Protocol (ARP) command line utility displays 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 for system administrators and is generally not a useful way to locate 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 remains the same.