A computer needs a Media Access Control (MAC) address and an IP address to function on the network. A MAC address is hard-coded to a machine's network card, so it is always available. The IP address is assigned using protocol drivers installed on a machine. If drivers or hardware fail on the computer, a MAC address is available but no IP is assigned to the network card.
The MAC and IP addresses work in conjunction to allow a computer to communicate over a network. The network routers, servers and client machines identify a computer using these two sets of numbers. The MAC address is hard-coded, so the network devices "trust" this number to accurately identify a machine. The IP address helps route communication packets to the machine. A computer's IP address can be dynamic or static, depending on the network configurations set by the administrator.
The MAC address is an alphanumeric value on the network card. An IP address can be static or dynamic. A static IP address is set in the computer's configuration, and it does not change even when the user reboots. An IP address must be unique on the network, or errors occur. The operating system reports an error, and the machine is kicked off the network. This can cause communication issues using the computer's IP address. A dynamic IP is assigned using a DHCP server. If the server is not configured properly, a computer may not have an IP address even when connected to the network.
An administrator can identify if the machine has an IP address. The "ping" command tells the administrator if an IP address is connected with the network card. Typing "ping machine_name" into the machine's command prompt returns an error if no IP address is present. If the ping command fails, check the network card to ensure the cable is connected to it.
The network card may have a MAC address, but no IP address if the card is malfunctioning. If other machines on the network receive an IP address from a DHCP server, check the network card by changing it out with another network card. This identifies if the network card's hardware no longer functions and a new one is necessary.
Network cards require drivers installed on the machine, so it can communicate with the operating system. If drivers are corrupted or the wrong drivers are installed, the network card has a MAC address but no IP address. Download new drivers from the manufacturer's website and reinstall them. This can fix software issues with the network card.
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