8-4

DHCP Server Operation

8.3.4 Options

DHCP (and also BOOTP with Vendor Extensions) provide a mechanism whereby the server can provide the client with information about how to configure its network interface (e.g., subnet mask), and also how the client can access various network services (e.g., IP routers). These options can be specified on a per-subnet basis, and, for BOOTP clients, also on a per-client basis. In the event that a BOOTP client declaration specifies options that are also specified in its subnet declaration, the options specified in the client declaration take precedence. A reasonably complete DHCP configuration would take the following form:

subnet 239.252.197.0 netmask 255.255.255.0 { range 239.252.197.10 239.252.197.250; default-lease-time 600;

max-lease-time 7200;

option subnet-mask 255.255.255.0; option broadcast-address 239.252.197.255; option routers 239.252.197.1;

}

Note that the DHCP client cannot use all the options given in RFC2132 to actually configure its own IP stack. However, the DHCP server can supply any of the options given there - this could be useful when using, for example, a DHCP server with several Microsoft® DHCP clients.

8.4 Configuration reference guide

The DHCP configuration file, dhcpd.conf, is a free-form ASCII text file. The file may contain extra tabs and newlines for formatting purposes. Keywords in the file are case-insensitive.

Comments may be placed anywhere within the file (except within quotes). Comments begin with the # character and end at the end of the line.

The file essentially consists of a list of statements. Statements fall into two broad categories – parameters and declarations.

Parameter statements indicate how to do something (e.g., duration of offered lease), whether to do something (e.g., provision of IP addresses to unknown clients), or what parameters to provide to the client (e.g., use gateway 220.177.244.7).

Declarations are used to describe the topology of the network, to describe clients on the network, to provide addresses that can be assigned to clients, or to apply a group of parameters to a group of declarations. In any group of parameters and declarations, all parameters must be specified before any declarations which depend on those parameters may be specified.

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IBM Heritage user manual Options, Configuration reference guide

Heritage specifications

IBM, or International Business Machines Corporation, is a global leader in technology and consulting, with a heritage that spans over a century. Established in 1911, IBM initially emerged from a merger of four companies, and it has since evolved into one of the most influential players in the tech industry.

One of the main features of IBM’s legacy is its commitment to innovation. The company has a long history of technological breakthroughs, including the development of the first programmable computer, the IBM 701, in the early 1950s. IBM has also been at the forefront of many pivotal technologies, including mainframe computers, which became central to large-scale enterprise computing. The System/360, introduced in 1964, revolutionized the industry by offering a compatible range of computers that could run the same software, a concept that helped define the standardization of computer systems.

IBM’s contributions to artificial intelligence, particularly through its Watson platform, are another hallmark of its heritage. Watson gained international fame for its success on the quiz show Jeopardy! in 2011, showcasing advanced natural language processing capabilities and machine learning techniques. This technology has since found applications in various fields, from healthcare to finance, significantly transforming data analysis.

Another key characteristic of IBM is its focus on research and development. With an impressive portfolio of patents, IBM consistently ranks among the top patent holders annually. Their research endeavors have led to significant advancements in quantum computing, with initiatives like the IBM Quantum Experience making quantum technologies accessible to developers and researchers.

Sustainability is also a priority for IBM, with programs aimed at promoting environmental responsibility. The company has committed to achieving net-zero greenhouse gas emissions by 2030, reflecting the growing importance of sustainability in technology practices.

In summary, IBM's heritage is characterized by a strong legacy of innovation, technological leadership, and a commitment to addressing contemporary challenges in business and society. From pioneering mainframe systems to leading the charge in AI and quantum computing, IBM continues to shape the future of technology while maintaining a visionary outlook towards a sustainable and inclusive digital world.