permanently connected to a network with adequate addresses available,
DHCP allocates infinite leases.
DHCP offers your network some advantages. First, it shifts responsibility for
assigning IP addresses from the network administrator (who can accidentally
assign duplicate IP addresses) to the DHCP server. Second, DHCP makes
better use of limited IP addresses. If a user is away from the office for
whatever reason, the user’s host can release its IP address for use by other
hosts.
Like most other things in life, DHCP is not perfect. Servers cannot be
configured through DHCP alone because DNS does not know what addresses
DHCP assigns to a host. This means that DNS lookups are not possible on
machines configured through DHCP alone; therefore, services cannot be
provided. However, DHCP can make assignments based on DNS entries
when using subnet/hostname or subnet/hardware address identifiers.
NOTE
The problem of using DHCP to configure servers using registered
hostnames is being addressed by Dynamic DNS, which, when fully
developed, will enable DHCP to register IP addresses with DNS. This will
enable you, for example, to register a domain name (such as
matthewhelmke.com) and be able to easily access that domain’s web server
without needing to use static IP addressing of a specific host. The largest
hurdle to overcome is the security implication of enabling each host
connecting to the system to update DNS. A few companies, such as
Dyn.com (www.dyndns.org), are already offering Dynamic DNS services
and have clients for Linux.Activating DHCP at Installation and Boot Time
Ubuntu automatically defaults your network interfaces to using DHCP
because it is the simplest way of setting up a network interface. With
dynamic, or DHCP-assigned IP addressing schemes for your NIC, the
broadcast address is set at 255.255.255.255 because dhclient, the DHCP
client used for IP configuration, is initially unaware of where the DHCP
server is located, so the request must travel every network until a server
replies.
You can find the instruction to use DHCP for your NIC in
/etc/network/interfaces, in a line that says dhcp.
Other settings specific to obtaining DHCP settings are saved in the file