Configure Each Subnet for DHCP

This section discusses using dhcpconfig to configure subnets, based on your responses to three questions for each subnet:

• What range of IP addresses do you want to be searched for unused IP addresses to allocate?

• Do you want the DHCP daemon to respond to requests for a specific subnet?

• For each monitored subnet, how many clients do you want to be assigned dynamically-allocated IP addresses?

How Each Subnet for DHCP is Configured

The dhcpconfig script creates a table--called the dhcp_network table--for each subnet being configured on the server system. The table name is the same as the IP address, but with decimal points replaced by underscores. For example, the subnet 129.148.5.0 has a dhcp_network table 129_148_5_0 in the name service being used by DHCP. For NIS+, this is a table in the org_dir object. For files, this is a file in the /var/dhcp directory.

Each client system being managed by DHCP has an entry in the dhcp_network table (the table corresponding to the subnet on which the client machine is attached). Entries may be permanent, with the IP address permanently assigned to the machine. Or, entries may be dynamic, where the DHCP server assigns an IP address when the client is first configured and provides a lease, a specified amount of time for which the IP address can be used. It is these dynamic clients that this step attempts to set up. Permanent clients can be set up with pntadm after the DHCP environment is fully configured.

Start the DHCP Service Daemon

This section describes three functions performed by the dhcpconfig script:

• Installs the start/stop script for the DHCP daemon processes into the /etc/init.d directory

• Sets up links to this script in the /etc/rc{0,3}.d directories

• Starts the daemon processes

The start/stop script is named dhcp and the links are S34dhcp (to start the daemons) and K34dhcp (to stop the daemons). This follows standard SVR4 procedure for daemon process execution at boot time.

One daemon process, in.dhcpd, is started. The in.dhcpd daemon is the DHCP server process, which responds to the client DHCP requests and forwards the network configurations, which have been established in the dhcptab table.