27.1. DHCP resource

27.1. DHCP resource
	Chapter 27. DHCP - Dynamic Host Configuration Protocol

The Abilis DHCP module implements three working modes:

BOOTP relay agent (Relay mode): internet host or router that passes DHCP messages between DHCP clients and DHCP servers.
DHCP Server: internet host that returns configuration parameters to DHCP clients.
DHCP Client: internet host which retrieves configuration parameters from a server.

27.1.1. Activating DHCP resource

Add the resource to the Abilis system with the following command.

[17:14:59] ABILIS_CPX:a res:dhcp

RES:DHCP ALREADY EXISTS

The DHCP resource may already exist in the system, but may not yet be active: set it active with the command:

[17:15:17] ABILIS_CPX:s act res:dhcp

COMMAND EXECUTED

	Caution
	After adding or setting the DHCP active, you must restart the Abilis to make the resource running (use the command warm start to reboot the Abilis).

[17:14:59] ABILIS_CPX:s p dhcp act:yes

COMMAND EXECUTED

[17:15:17] ABILIS_CPX:d p dhcp

RES:Dhcp - Not Saved (SAVE CONF), Not Refreshed (INIT) ------------------------
       ------------------------------------------------------------------------
Run    DESCR:Dynamic_Host_Configuration_Protocol
       LOG:DS           ACT:YES       srv-udp-locport:67   cli-udp-locport:68
       msg-len:1472     mode:RELAY    MAX-HOPS:4     SRV:#
       LOCIPADD:R-ID (192.168.001.001)
       WDIR:C:\APP\DHCP\

27.1.2. DHCP resource parameters

Use the following command to display the parameters of the resource; by typing d p dhcp ? command, the meaning of all parameters is shown.

[17:15:17] ABILIS_CPX:d p dhcp

RES:Dhcp ----------------------------------------------------------------------
Run    DESCR:Dynamic_Host_Configuration_Protocol
       LOG:DS           ACT:YES       srv-udp-locport:67   cli-udp-locport:68
       msg-len:1472     mode:RELAY    MAX-HOPS:4     SRV:#
       LOCIPADD:R-ID (192.168.001.001)
       WDIR:C:\APP\DHCP\

Meaning of the most important parameters:

LOG: Logging functionalities activation/deactivation.
ACT: Runtime DHCP activation/deactivation.
srv-udp-locport: Server side UDP port [default is 67].
cli-udp-port: Client side UDP port [default is 68].
msg-len: Maximum length of DHCP message, actually the UDP payload [548..2048];
mode: It specifies the mode of DHCP port working [SERVER, RELAY].

Parameters for mode:RELAY only:

MAX-HOPS: It specifies the maximum number of DHCP relay agent hops.
SRV: It specifies the DHCP Server to which requests must be forwarded; it can be set to an IP address, in Dotted Decimal Notation, or the name of an IP list;
LOCIPADD: It specifies the IP address that DHCP relay agent will use as “source address” in the requests relayed to the server.

Parameters for mode:SERVER only:

max-clients: Maximum number of supported DHCP clients; it actually determines the size of the binding database on disk and in memory.
ICMPCHK: Enables ICMP checking of IP address. When it is set to YES, ICMP checking is enabled. Before sending the DHCPOFFER message, the server sends two ICMP ping requests to check the IP address which was allocated. If both timeouts expire, the server will send the DHCP offer message, otherwise it will mark this IP address as abandoned and will not send response.
MAC-FILTER: Enables/disables the selection of serviceable clients based on their MAC address. When it is set to YES, MAC filtering is enabled. When DHCP receives an incoming request and before processing it, the DHCP verifies that the sender's MAC address is allowed by using MAC-LIST and MAC-RULE parameters current setting (MAC-LIST and MAC-RULE appear when MAC-FILTER is set to YES).
WDIR: Selects the directory where DHCP.BND (BND stays for binding) file is saved. A binding is a collection of configuration parameters, including at least an IP address, associated with or “bound to” a DHCP client. Bindings are managed by DHCP servers.

The following command allows the administrator to change the configuration of the resource:

s p dhcp parameter:value...

	Caution
	To activate the changes made on the upper case parameters, execute the initialization command init res:dhcp; while to set act the changes made on the lowercase parameters a save conf and an Abilis restart are required (i.e. With warm start command).


Chapter 27. DHCP - Dynamic Host Configuration Protocol		27.2. DHCP Relay Mode