An IP lease ensures the recovery of
unused IP addresses to the pool of available IP addresses. The time limit
ensures that the host is still alive and connected to the network. Scavenging
is the process by which a DNS server will purge stale record. The server sets
the span of time for which it considers a record stale. It then will remove the
record to prevent multiple hostnames pointing to the same IP address. The
option “Obtain an IP address automatically” sets the network interface to
obtain its IP address, gateway, and DNS server from a DHCP server.

DHCP and DNS are two systems that
require integration to prevent IP collisions. When the DHCP server changes the
IP address of a host it must update the associated DNS record to sure proper name
resolution. This accomplished through dynamic updating of the DNS server. The
process used to accomplish this depends on the setup. A DHCP server can send
the update or the client itself can send the update or the PTR/A records.

Dynamic DNS is more commonly talked about when registering a Domain name with a
dynamic IP address. This can be accomplished through software that sits on a
router or host and send a DNS server the current IP address of the network.