Setting up a server is often required to provide a specific function
or service. Most of the time, said services are implemented to centrally manage
data, add messaging and collaboration to an enterprise, or establish a web
presence on the Internet.

However, most of these services would not be possible
without a server running the Dynamic Host Control Protocol (DHCP) — and DNS, which will be the focus of my next
article — on the LAN, since it manages the pool of IP addresses
assigned to network devices and is directly related to getting clients online
and communicating.

Setting
up DHCP

  1. Open the Server.app application (Figure A).
    Figure A
  2. Login to the server management console with an
    administrative account (Figure B).
    Figure B
  3. Click on DHCP under Services to bring up the DHCP management pane (Figure C).
    Figure C

Managing DHCP Networks

You’ll notice two tabs, Networks and Clients,
with a range of IP addresses created by default
when Open Directory is first created. The Networks tab is used to contain a list of IP address range(s) for your specific network.
The protocol will automatically assign IP addresses to network-based devices as
they go online and request one from DHCP.  

  1. On the Networks tab, use the plus sign [+], minus sign [-], and pencil icon to add, remove, or edit a range listing. Click the plus sign [+] to add a new IP range (Figure
    D    ) with the specific range assigned to your enterprise (Figure E).
    Figure D

    Figure E
  2. Once all the information has been added, you can
    specify the IP address(es) of DNS server(s) in the event that you wish to
    assign certain DNS servers to specific IP ranges (for example, managing multiple sites can be addressed by creating a
    DHCP range for each site and assigning a specific DNS server IP to each site’s
    range, if necessary — as in Figure F).
    Figure F
  3. Highlighting a range and clicking the minus sign [-] or pencil
    icon will remove or allow you to edit that specific IP range.
  4. Click Done to commit changes to Open Directory, and click the ON/OFF switch to ON to
    start the DHCP service. *

Managing
DHCP Clients

  1. The Clients tab of the DHCP service pane is
    used to manage statically assigned IP addresses to nodes based on the MAC
    address on the network card (Figure G).
    Figure G
  2. Use the plus sign [+], minus sign [-], and pencil icon to add, remove, or edit a static entry. Click the plus sign [+] to add a new static IP
    entry by associating the address with the MAC address of the specific device (Figure H).
    Figure H
  3. Under the Network section, select the DHCP range to associate with the device, and then click Done to commit the changes to DHCP and
    OD.

* Note: When starting the DHCP service, ensure
that no other conflicting DHCP services are running on the network, as issues
will arise almost immediately and negatively impact all network devices that
are relying on IP addresses to obtain online connectivity. If OS X Server
discovers another potential instance of DHCP running on the LAN, it’ll prompt
you to confirm prior to activating the DHCP service (Figure I).

Figure I

Dynamically assigning IPs is one of those services that are
fundamental to the enterprise. It’s something so simple and lightweight — yet, without it, medium- to large-scale IT departments would be hard pressed by
having to physically keep track of and visit each and every network-capable
device and manually configure them. While the process is less cumbersome for small office/home office (SOHO)
environments, it steals precious time away from productivity.

DHCP is an infinitely more efficient method of managing
addresses and, to a greater extent, managing connectivity at multiple sites by keeping
the ranges split up. Coupled with assigned names servers, system access to such
resources could be load-balanced or, at the very least, easy to restore in the
event of a service outage.