Automatic Private IP Addressing
Automatic Private IP Addressing (APIPA) is a
feature of Windows clients and servers that allows systems on the same
network to automatically establish network connectivity and
communication with one another when no DHCP server is available. This
is a great feature for a very small network where a set of machines
need to share data and communicate with one another with little or no
IT support. The IP addresses automatically assigned to adapters with
this configuration are in the 169.254.0.0/16 subnet range. APIPA is
enabled on all Windows clients by default. When a Windows client cannot
locate a DHCP server and assigns itself with an automatic private IP
address, it may not readily detect when a DHCP server comes online and
may remain off the network unnecessarily long. APIPA cannot be disabled
on Windows 8 and Windows Server 2012 systems except by disabling DHCP
altogether.
DHCP Relay Agents
A DHCP relay agent can play a
critical role on an enterprise network, allowing DHCP services to be
extended across routers and different networks. When a DHCP client
broadcasts a DHCP client broadcast, that broadcast is normally only
allowed on the local network, which means that if there is no local
DHCP server, there is no DHCP server response. Two ways to circumvent
this limitation, or really this feature, is to either locate a DHCP
server in each network or configure a DHCP relay agent on each remote
network. The role of a DHCP relay agent is to pick up the local DHCP
client broadcast and to forward that request to a designated DHCP
server on a remote network. The remote DHCP server must, of course, be
configured with a scope of IP addresses for that network, and when
responding provides that lease information to the DHCP relay agent,
which delivers that information to the client. This allows for DHCP
services to be located centrally and managed by Windows Server 2012
systems, while the DHCP relay agent service can be provided by Windows
clients, servers, or network devices such as switches, routers, or
firewalls.
DHCP and Dynamic DNS Integration
The Windows Server 2012 DHCP service provides
direct integration with the Dynamic DNS (DDNS). All Windows clients and
servers are configured by default to register their name and IP address
with the designated domain name system (DNS) server as configured
manually or by DHCP on their respective network card IP settings. When
a DNS server is configured to allow networking clients to automatically
register their records within DNS zones, this functionality is referred
to as Dynamic DNS registration. With a Windows Server 2012 DHCP server,
this functionality can be extended to not only Windows clients leasing
an IP address from the DHCP server but to any DHCP client. The DHCP
server can, in fact, register the name and IP address on the DNS zone
on behalf of the client using its own server computer account or a
specified user account that has been granted rights to register DNS
records.
Installing DHCP Server and Server Tools
The DHCP role can be installed on a Windows
Server 2012 system at any time using the Server Manager console. If the
DHCP server tools are required on the local DHCP server, they can be
selected for installation during the role installation or at a later
time. Ideally, IT shops now are making the move toward centralized
management, and this in many cases means no management tools on each
server. To install the DHCP role and server tools on a single system,
follow these steps:
1. Log on to the proposed DHCP server.
2. Click the Server Manager tile on the taskbar.
3. When the Server
Manager console opens, on the Welcome to Server Manager page, click Add
roles and features in the right pane, as shown in Figure 1.
Figure 1. Starting the Add Roles and Features Wizard from the Server Manager.
4. On the Before You Begin page, in the Add Roles and Features Wizard, click Next to continue.
5. On the Select
Installation Type page, select the Role-based or Feature-based
Installation radio button, and then click Next to continue.
6. On the Select
Destination Server page, select the Select a Server from the Server
Pool radio button and select the local server in the window. Click Next
to continue.
7. On the Select
Server Roles page, check the DHCP Server role, and in the Add Roles and
Features Wizard pop-up window, click Add Features to also install the
DHCP Server Tools. Click Next to continue.
8. On the Select
Features page, scroll down to the Remote Server Administration Tools
Features group, expand it, and expand the Role Administration Tools
group and verify that the DHCP Server Tools Feature is also selected.
Then click Next to continue.
9. On the DHCP Server page, read the information and click Next to continue.
10. On the Confirm
Installation Selections page, click Install to begin the installation.
If a reboot is required, you are prompted after the installation
completes. Reboot as required.
11. From the Installation Progress page, you can monitor the installation progress, but do not close the window.
12. When the installation completes, click the Complete DHCP Configuration link on the Installation Progress page, as shown in Figure 2.
Running this wizard creates the DHCP Administrators and the DHCP Users
security group on the local machine and authorizes this server in
Active Directory.
Figure 2. Launching the DHCP Post-Install Wizard.
13. On the Description page of the DHCP Post-Install Wizard, click Next to continue.
14. On the
Authorization page, if the current logon account has the rights to
authorize this server in Active Directory, click Commit to complete the
task. If another account is required, enter the appropriate credentials
and click Commit.
15. On the Summary
page, verify the security groups were created and that authorization
has completed. Click Close in the Post-Install Wizard window and click
Close again in the Add Roles and Features Wizard window.
After the installation completes, you are
returned to the Server Manager window. This Post-Install Wizard
includes authorizing the DHCP server and creating the local groups DHCP
Administrators and DHCP Users for DHCP server delegation.
DHCP authorization is the process of
registering a new server in Active Directory to allow it to provide
DHCP services on the network. This wizard should be run after all DHCP
server installations. However, if DHCP server authorization is not
necessary, skip authorization and just let the wizard create the
delegation groups.
This completes the DHCP server and server tools installation task.
