Under what condition would a DHCP server lease an IP address to a client?

A DHCP server leases an IP address to a client when it receives a request from a valid MAC address. Each network interface card (NIC) has a unique MAC address that identifies its device on the network. When a device connects to a network and requests an IP address, it sends a DHCPDISCOVER message containing its MAC address. The DHCP server uses this information to determine whether the client is valid and can be assigned an IP address from its available pool.

In this process, the DHCP server checks its database for existing leases related to that MAC address. If it finds that the MAC address is valid and the client hasn't exceeded its leased time or reached any limitations, it responds with a DHCPOFFER that includes the available IP address. This ensures that the DHCP server has a systematic way of managing IP assignments, preventing conflicts and ensuring that each device on the network receives unique IP addresses as intended.