DHCP lease
Networking
The temporary allocation a DHCP server grants a machine, after the four messages Discover, Offer, Request and Acknowledge — the first broadcast, since a machine with no address can receive no reply. The lease delivers much more than an address: the prefix, the gateway and the resolver addresses arrive with it, which is why a failed DHCP so often presents as "DNS is broken". ip -o -4 addr show marks it dynamic and counts its validity down in valid_lft; an address set by hand reads forever. On Ubuntu 24.04 the client is systemd-networkd, not dhclient, which the release no longer ships.
Also written: DHCP, DORA, valid_lft