2. Dynamic Host Configuration Protocol (DHCP) is a client/server protocol that automatically provides an Internet Protocol (IP) host with its IP address and other related configuration information such as the subnet mask and default gateway. define DHCP as an Internet Engineering Task Force (IETF) standard based on Bootstrap Protocol (BOOTP), a protocol with which DHCP shares many implementation details. DHCP allows hosts to obtain necessary TCP/IP configuration information from a DHCP server.
3. A user turns on a computer with a DHCP client. The client
computer sends a broadcast request (called a DISCOVER or
DHCPDISCOVER), looking for a DHCP server to answer,
The router directs the DISCOVER packet to the correct
DHCP server.
The server receives the DISCOVER packet. Based on
availability, and usage policies set on the server, the server
determines an appropriate address (if any) to give to the
client. The server then temporarily reserves that address
for the client and sends back to the client an OFFER (or
DHCPOFFER) packet, with that address information. The
server also configures the client's DNS servers,WINS
servers, NTP servers, and sometimes other services as well.
.
4. The client sends a REQUEST (or DHCPREQUEST) packet, letting the server know that it intends to use the address.
The server sends an ACK (or DHCPACK) packet, confirming that the client has a been given a lease on the address for a server-specified period of time.
When a computer uses a static IP address, it means that the computer is manually configured to use a specific IP address. One problem with static assignment, which can result from user error or inattention to detail, occurs when two computers are configured with the same IP address. This creates a conflict that results in loss of service. Using DHCP to dynamically assign IP addresses minimizes these conflicts.
5. What's New in DHCP for Server 2012?
Each new generation Windows server brings yet more options for DHCP configuration, these are the highlights of new DHCP features in Windows Server 2012.
PowerShell for DHCP
DHCP Policy Assign
DHCP Failover
6. PowerShell for DHCP
Windows Server 2012 provides task-oriented Windows PowerShell
cmdlets for DHCP server management. The DHCP server configuration
operations are implemented in Windows Server 2012 as Common
Information Model (CIM) based cmdlets. Windows PowerShell uses
object pipelining to eliminate the need for parsing and manipulation of
text output. Windows PowerShell for DHCP Server includes 103
cmdlets, covering multiple aspects of DHCP server configuration and management.
DHCP Policy Assign
With policy based assignment, the DHCP the server evaluates
DHCP requests against policies that you define. Policies are
applicable for a specific scope with a defined processing order. Policies
applicable at a scope can be configured at the scope or inherited from
server wide policies. A single client request can match multiple
policies, and policies can be associated with multiple address ranges.
For more information about DHCP policy based assignment,
7. DHCP Failover
This feature provides the ability to have two DHCP servers serve
IP addresses and option configuration to the same subnet or
scope, providing for continuous availability of DHCP service to
clients. The two DHCP servers replicate lease information
between them, allowing one server to assume responsibility for
servicing of clients for the entire subnet when the other server is
unavailable. It is also possible to configure failover in a load-
balancing configuration with client requests distributed between
the two servers in a failover relationship. For more information
about DHCP failover,
8. Why use DHCP
Every device on a TCP/IP-based network must have a unique unicast
IP address to access the network and its resources. Without DHCP, IP
addresses must be configured manually for new computers or
computers that are moved from one subnet to another, and manually
reclaimed for computers that are removed from the network.
DHCP enables this entire process to be automated and managed
centrally. The DHCP server maintains a pool of IP addresses and leases
an address to any DHCP-enabled client when it starts up on the
network. Because the IP addresses are dynamic (leased) rather than
static (permanently assigned), addresses no longer in use are
automatically returned to the pool for reallocation.
The network administrator establishes DHCP servers that maintain
TCP/IP configuration information and provide address configuration to
DHCP-enabled clients in the form of a lease offer. The DHCP server stores
the configuration information in a database, which includes:
9. Valid TCP/IP configuration parameters for all clients on the network.
Valid IP addresses, maintained in a pool for assignment to clients, as well as excluded addresses.
Reserved IP addresses associated with particular DHCP clients. This allows consistent assignment of a single IP address to a single DHCP client.
The lease duration, or the length of time for which the IP address can be used before a lease renewal is required.
A DHCP-enabled client, upon accepting a lease offer, receives:
A valid IP address for the subnet to which it is connecting.
Requested DHCP options, which are additional parameters that a DHCP server is configured to assign to clients. Some examples of DHCP options are Router (default gateway), DNS Servers, and DNS Domain Name. For a full list of DHCP option
10. Summary of Windows Server 2012 DHCP
Configuring DHCP server is fun. Windows 2012 introduces
numerous PowerShell cmdlets not only to add the DHCP role,
but also to configure the scopes. The benefit of DHCP is that
once up and running you don't need to worry about clients
machines getting the right IP address. Furthermore if you need
to change the IP address of a key router or server, then the
clients machine automatically receive the update.
