Can MAC Addresses Be Converted to IP Addresses?

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A MAC address represents the physical identifier of a network adapter, while the IP address represents a logical device address on TCP/IP networks. Only in certain specific situations can a client user identify the IP address associated with an adapter when knowing only its MAC address.

ARP and Other TCP/IP Protocol Support for MAC Addresses

Now obsolete TCP/IP protocols called RARP (Reverse ARP) and InARP could identify IP addresses from MAC addresses.

 Their functionality is part of DHCP. While the internal workings of DHCP manage both MAC and IP address data, the protocol does not allow users to access to that data.

A built-in feature of TCP/IP, Address Resolution Protocol (ARP) translates IP addresses to MAC addresses. ARP was not designed to translate addresses in the other direction, but its data can help in certain situations.

ARP Cache Support for MAC and IP Addresses

ARP maintains a list of both IP addresses and matching MAC addresses called the ARP cache. These caches are available on individual network adapters and also on routers. From the cache it is possible to derive an IP address from a MAC address; however, the mechanism is limited in many respects.

Internet Protocol devices discover addresses through Internet Control Message Protocol (ICMP) messages (such as those triggered by the use of ping commands). Pinging a remote device from any client will trigger an ARP cache update on the requesting device.

On Windows and some other network operating systems, the "arp" command provides access to the local ARP cache. In Windows, for example, typing "arp -a" at the command (DOS) prompt will display all of the entries in that computer's ARP cache. This cache may be empty sometimes depending on how that local network is configured, At best, a client device's ARP cache only contains entries for other computers on the LAN.

Most home broadband routers allow viewing of their ARP caches through their console interface. This feature reveals both IP and MAC addresses for every device currently joined to the home network. Note that routers do not maintain IP-to-MAC address mappings for clients on other networks beside their own. Entries for remote devices can appear in the ARP list but the MAC addresses shown be for the remote network's router, not for the actual client device behind the router.

Management Software for Device Addressing on Business Networks

Larger business computer networks solve the problem of universal MAC-to-IP address mapping by installing special management software agents on their clients. These software systems, based on Simple Network Management Protocol (SNMP), include a capability called network discovery. These systems forward messages out to the agent on every network device a request for both the IP and MAC addresses of that device. The system receives then stores the results in a master table separate from any individual ARP cache.

Corporations that have full control over their private intranets use network management software as a (sometimes expensive) way to manage the client hardware (that they also own).

 Ordinary consumer devices like phones don't have SNMP agents installed, no do home network routers function as SNMP consoles.

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