When it moves from the ISP’s router to another router on the internet, it contains the MAC address of the ISP’s router. When your router sends the information further upstream to your ISP’s router, it contains the MAC address of your router. But when it arrives at your router, that MAC address is removed. That means when information leaves your computer, it has your computer’s network adapter’s MAC address. While the IP addresses involved indicate the original source 3 and ultimate destination, a MAC address is used only on connections from one piece of networking equipment to the next. The MAC address is used by the network to identify which piece of hardware a packet of information is to be sent to. So the uniqueness on which we might want to rely is not 100% reliable.īut that isn’t really the biggest problem. Some operating systems now randomize the MAC address.In many network interfaces, the MAC address can be set in software - meaning whatever the original MAC address, it can be changed.Occasionally, manufacturers don’t ensure they’re unique, so multiple network interfaces can have the same MAC address.In theory, every network card or network interface should have its own unique MAC address, different from every other network card or interface on the planet. If your computer has multiple network interfaces - say both a wired ethernet port and a wireless network adapter - each interface will have its own MAC address.

MAC addresses are unique - sort ofĪ Media Access Control (or MAC 1) address is a unique 48-bit number 2 assigned to every network interface. That limits the usefulness of MAC addresses for any kind of device location or tracing. While they do identify the device, when used in networking they travel only as far as the next device, like your router. MAC addresses are unique identifiers for each network interface on your device.

How to find mac id of laptop