anchor.diff:  === DhcpMonitor
   
   This monitor is used to monitor the availability and functionality of http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol[DHCP servers].
  -This monitor has two parts, the first one is the monitor _DHCP_ executed by _Pollerd_ and the second part is a background daemon _Dhcpd_ listening for DHCP responses.
  -A DHCP server is tested by sending a _DISCOVER_ message, if the DHCP server responds with an _OFFER_ the service is marked as up.
  -The _Dhcpd_ background daemon is disabled by default and has to be activated in the 'service-configuration.xml' in OpenNMS by changing `service enabled="true"`.
  +This monitor has two parts, the first one is the monitor class _DhcpMonitor_ executed by _Pollerd_ and the second part is a background daemon _Dhcpd_ running inside the OpenNMS JVM and listening for DHCP responses.
  +A DHCP server is tested by sending a _DISCOVER_ message. If the DHCP server responds with an _OFFER_ the service is marked as up.
  +The _Dhcpd_ background daemon is disabled by default and has to be activated in 'service-configuration.xml' in OpenNMS by setting `service enabled="true"`.
   The behavior for testing the DHCP server can be modified in the 'dhcp-configuration.xml' configuration file.
   
   IMPORTANT: It is required to install the `opennms-plugin-protocol-dhcp` before you can use this feature.
  
positive.code: <monitor service="DHCP" class-name="org.opennms.protocols.dhcp.monitor.DhcpMonitor"/>
  ----
  
  .Step 2: Enable the OpenNMS _Dhcpd_ background daemon in 'service-configuration.xml'
  [source, xml]
  ----
  <service enabled="true">
  
negative.code: 
  ===== _Dhcpd_ configuration
  
  ._Dhcpd_ parameters in 'dhcp-configuration.xml'.
  [options="autowidth"]
  |===
  | Parameter          | Description                                                                       | Required           | Default value
  | `port`             | Defines the port your dhcp server is using                                        | required           | `5818`
  | `macAddress`       | The MAC address which OpenNMS uses for a dhcp request                             | required           | `00:06:0D:BE:9C:B2`
  | `myIpAddress`      | This parameter will usually be set to the IP address of the OpenNMS server,
                         which puts the DHCP poller in `relay` mode as opposed to `broadcast` mode.
                         In `relay` mode, the DHCP server being polled will unicast its responses directly
                         back to the IP address specified by `myIpAddress` rather than broadcasting its
                         responses. This allows DHCP servers to be polled even though they are not on the
                         same subnet as the OpenNMS server, and without the aid of an external relay.
                         _Usage:_ `myIpAddress="10.11.12.13"` or `myIpAddress="broadcast"`                 | required           | `broadcast`
  