There are three ways that a DHCP server either assigns
or sends an IP address to a client:
—The DHCP server assigns a
permanent IP address to a client from its
On the firewall, a
the allocation is permanent.
—The DHCP server assigns a reusable
IP address from
of addresses to
a client for a maximum period of time, known as a lease.
This method of address allocation is useful when the customer has
a limited number of IP addresses; they can be assigned to clients
who need only temporary access to the network. See the DHCP
—The network administrator chooses
the IP address to assign to the client and the DHCP server sends
it to the client. A static DHCP allocation is permanent; it is done
by configuring a DHCP server and choosing a
to correspond to the
the client device. The DHCP assignment remains in place even if
the client logs off, reboots, has a power outage, etc.
allocation of an IP address is useful, for example, if you have
a printer on a LAN and you do not want its IP address to keep changing,
because it is associated with a printer name through DNS. Another
example is if a client device is used for something crucial and
must keep the same IP address, even if the device is turned off,
unplugged, rebooted, or a power outage occurs, etc.
points in mind when configuring a
It is an address from the
You may configure multiple reserved addresses.
If you configure no
the clients of the server will receive new DHCP assignments from
the pool when their leases expire or if they reboot, etc. (unless
you specified that a
If you allocate all of the addresses in the
there are no dynamic addresses free to assign to the next DHCP client requesting
You may configure a
. In this case,
the DHCP server will not assign the
any device. You might reserve a few addresses from the pool and
statically assign them to a fax and printer, for example, without