CHGDHCPA (Change DHCP Attributes) Command

Purpose

The Change DHCP Attributes (CHGDHCPA) command is used to change the startup attributes of the Dynamic Host Configuration Protocol (DHCP) server. The changes take effect the next time the DHCP server is started either by the Start TCP/IP (STRTCP) command or by the Start TCP/IP Server (STRTCPSVR) command.

Note: If the STRTCPSVR(*ALL) command is issued, all TCP/IP servers that have been configured will start. However, the BOOTP and DHCP servers cannot both run on the same machine at the same time. If the STRCPRSVR(*ALL) command is issued, the system will first check to see if both a BOOTP and DHCP server job is configured. If both are configured, the system checks the AUTOSTART attributes for each server.

If one of the servers (BOOTP or DHCP) AUTOSTART attributes is set to *YES and other is set to *NO, the server with AUTOSTART attributes set to *YES will start.

If both servers (BOOTP or DHCP) AUTOSTART attributes are set to *NO, the DHCP server will start.

You cannot set the DHCP AUTOSTART attribute to *YES if the BOOTP AUTOSTART value is set to *YES. A BOOTP and DHCP server cannot run simultaneously on the same machine.

Restrictions: You must have *IOSYSCFG special authority to use this command.

Required Parameters

AUTOSTART Specifies whether to automatically start the DHCP server when TCP/IP is started by the STRTCP command. The STRTCPSVR command will use the AUTOSTART parameter value if SERVER(*ALL) is specified on the start command.

*SAME: The AUTOSTART value does not change if it was previously set. Otherwise, *NO is used.

*YES: Start the DHCP server when the STRTCP command is called. *YES will not be allowed if the BOOTP server AUTOSTART attribute has been set to *YES by the CHGBPA command.

*NO: Do not start the DHCP server when the STRTCP command is called. If you do not intend to use the DHCP server, set AUTOSTART to *NO.

MODE Specifies whether DHCP on this system should be run as a functional Dynamic Host Configuration Protocol (DHCP) Server, or whether it should run as a BOOTP/DHCP Relay Agent.

*SAME: The MODE value does not change if it was previously set. Otherwise, *SERVER is used.

*SERVER: DHCP should run as a functional Dynamic Host Configuration Protocol (DHCP) Server on this system.

*RELAY: DHCP should run as a BOOTP/DHCP Relay Agent on this system.

Examples

Example 1: Start the DHCP Server Automatically

CHGDHCPA AUTOSTART(*YES)

This command indicates that the next time the STRTCP command is issued to start up TCP/IP and to automatically start the TCP/IP applications, the DHCP Server will be started automatically.

Example 2: Have DHCP Function as a BOOTP/DHCP Relay Agent

CHGDHCPA AUTOSTART(*SAME) MODE(*RELAY)

This command indicates that the next time the DHCP Server gets started, it should function as a BOOTP/DHCP Relay Agent. It will no longer attempt to process DHCP packets on the local system, but will instead relay them. If DHCP is currently running, this command has no affect on its current execution mode, since CHGDHCPA attributes do not take affect until the next time the server is started. And in this example, there is no change as to whether DHCP automatically starts with the rest of TCP/IP or not.

Example 3: Only Allow DHCP Server to be Started Manually

CHGDHCPA AUTOSTART(*NO) MODE(*SERVER)

This command indicates that the DHCP Server should not be started automatically with the rest of TCP/IP when the STRTCP command is issued. It can only be started manually via the STRTCPSVR command. Via the MODE setting of *SERVER, this example is also causing the DHCP server to attempt to process all DHCP packets received on this system.