This 48-bit address space contains potentially 2 48 (over 281 trillion) possible MAC addresses. The IEEE 802 MAC address originally comes from the Xerox Network Systems Ethernet addressing scheme. The b0 bit distinguishes multicast and unicast addressing and the b1 bit distinguishes universal and locally administered addressing.

However, two NICs connected to two different networks can share the same MAC address. Network nodes with multiple network interfaces, such as routers and multilayer switches, must have a unique MAC address for each NIC in the same network. MAC addresses are formed according to the principles of two numbering spaces based on Extended Unique Identifiers (EUI) managed by the Institute of Electrical and Electronics Engineers (IEEE): EUI-48-which replaces the obsolete term MAC-48-and EUI-64. The address typically includes a manufacturer's organizationally unique identifier (OUI). Many network interfaces, however, support changing their MAC address. Each address can be stored in hardware, such as the card's read-only memory, or by a firmware mechanism. MAC addresses are primarily assigned by device manufacturers, and are therefore often referred to as the burned-in address, or as an Ethernet hardware address, hardware address, or physical address. As typically represented, MAC addresses are recognizable as six groups of two hexadecimal digits, separated by hyphens, colons, or without a separator. Within the Open Systems Interconnection (OSI) network model, MAC addresses are used in the medium access control protocol sublayer of the data link layer. This use is common in most IEEE 802 networking technologies, including Ethernet, Wi-Fi, and Bluetooth. In any case, the best way to know 'who is connected' is to ask the device they're connected to.Label of a UMTS router with MAC addresses for LAN and WLAN modulesĪ media access control address ( MAC address) is a unique identifier assigned to a network interface controller (NIC) for use as a network address in communications within a network segment. The first solution requires parsing a web page and the second requires getting a plain text file from the router and parsing it. (the location may change but /tmp is pretty common). You can also get it from /tmp/dnsmasq.leases (on the router) if you're running a router that uses dnsmasq. You can scrape the page with your app and get a list of all currently active DHCP leases. Many routers display the current DHCP leases on a management page. The short least time will auto-renew whenever it expires as long as the client is still there.

The very easiest way to do this that I can come up with is to set your router's DHCP lease time to something short like 10 minutes, then ask the router 'who is connected'. OK, I've removed a bunch of stuff I said, now that I understand you're talking about cell phones and wifi connections. If you're on a multi-hop network, it's useless. MAC addresses are stripped off at the first router/switch, so they're not going to be useful for determining what is connected, unless you can access the monitoring port on your router/switch and you only have one.

Check mac address on network