Lesson 2 - Static and Dynamic IP Addressing

This lesson introduces you to the concepts of static and dynamic IP addressing. IP addresses can be set on a computer either statically or dynamically. Each method has pros and cons and must be managed differently. After completing this lesson, you should understand the differences between static and dynamic IP addressing.

About Dynamic Addressing DHCP

DHCP is the standard technology used to assign dynamic IP addresses. When setting up dynamic IP addressing on Windows or other operating systems, the "DHCP option" must be enabled. DHCP is technically a separate network protocol from IP. Definition: DHCP allows a computer to join an IP-based network without having a pre-configured IP address. DHCP is a protocol that assigns unique IP addresses to devices, then releases and renews these addresses as devices leave and re-join the network. Internet Service Providers (ISPs) usually use DHCP to allow customers to join the Internet with minimum effort. Likewise, home network equipment like broadband routers offers DHCP support for added convenience in joining home computers to the LAN. DHCP environments require a DHCP server set up with the appropriate configuration parameters for the given network. Key DHCP parameters include the range or "pool" of available IP addresses, the correct subnet masks, plus gateway and name server addresses. Devices running DHCP client software can then automatically retrieve these settings from DHCP servers as needed. Using DHCP on a network means system administrators do not need to configure these parameters individually for each client device.

APIPA On Windows computers, APIPA works together with DHCP to assign dynamic IP addresses. Definition: A feature of Microsoft Windows, APIPA is a DHCP failover mechanism for local networks. With APIPA, DHCP clients can obtain IP addresses when DHCP servers are non-functional. APIPA exists in all modern versions of Windows except Windows NT. When a DHCP server fails, APIPA allocates IP addresses in the private range 169.254.0.1 to 169.254.255.254. Clients verify their address is unique on the network using ARP. When the DHCP server is again able to service requests, clients update their addresses automatically. In APIPA, all devices use the default network mask 255.255.0.0 and all reside on the same subnet. APIPA is enabled on all DHCP clients in Windows unless the computer's Registry is modified to disable it. APIPA can be enabled on individual network adapters. Also Known As: Automatic Private IP Addressing; AutoNet Examples: Because APIPA uses IP addresses in the private Class B space, APIPA is a feature generally only useful on home or other small intranet LANs. ISP ISPs generally assign dynamic IP address to their customers. You can sometimes request static IP addressing from your ISP, at an extra cost. Definition: An ISP is a company that supplies Internet connectivity to home and business customers. ISPs support one or more forms of Internet access, ranging from traditional modem dial-up to DSL and cable modem broadband service to dedicated T1/T3 lines. More recently, wireless Internet service providers or WISPs have emerged that offer Internet access through wireless LAN or wireless broadband networks. In addition to basic connectivity, many ISPs also offer related Internet services like email, Web hosting and access to software tools. A few companies also offer free ISP service to those who need occasional Internet connectivity. These free offerings feature limited connect time and are often bundled with some other product or service. Subnet Definition: A subnet is a logical grouping of connected network devices. Nodes on a subnet tend to be located in close physical proximity to each other on a LAN. Network designers employ subnets as a way to partition networks into logical segments for greater ease of administration. When subnets are properly implemented, both the performance and security of networks can be improved. In Internet Protocol (IP) networking, devices on a subnet share contiguous ranges of IP address numbers. A mask (known as the subnet mask or network mask) defines the boundaries of an IP subnet. The correspondence between subnet masks and IP address ranges follows defined mathematical formulas. IT professionals use subnet calculators to map between masks and addresses.

We will have our next lesson of networking soon.