Windows 7 / Networking

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Assigning IPv4 addresses

In addition to understanding how IP addressing works, a network administrator must be familiar with the methods for deploying IP addresses to the computers on a network.

To assign IPv4 addresses, there are three basic alternatives:

• Manual configuration
• Dynamic Host Configuration Protocol (DHCP)
• Automatic Private IP Addressing (APIPA)

The advantages and disadvantages of these methods are discussed in the following sections.

MANUAL IPV4 ADDRESS CONFIGURATION

Configuring a TCP/IP client manually is not terribly difficult, nor is it very time-consuming. Most operating systems provide a graphical interface that enables you to enter an IPv4 address, a subnet mask, and various other TCP/IP configuration parameters. To configure IP address settings in Windows Server 2012, you use the Internet Protocol Version 4 (TCP/IPv4) Properties sheet.

When you select the Use The Following IP Address option, you can configure the following IP address options:

• IP Address: Specifies the IP address on the local subnet that will identify the network interface in the computer
• Subnet Mask: Specifies the mask associated with the local subnet
• Default Gateway: Specifies the IP address of a router on the local subnet, which the system will use to access destinations on other networks
• Preferred DNS Server: Specifies the IP address of the DNS server the system will use to resolve host names into IP addresses

The primary problem with manual configuration is that a task requiring two minutes for one workstation requires several hours for 100 workstations and several days for 1,000. Manually configuring all but the smallest networks is highly impractical, and not just for reasons of time. There is also the matter of tracking the IPv4 addresses you assign and making sure each system has an address that is unique. This can end up being a logistical nightmare, which is why few network administrators choose this option.

DYNAMIC HOST CONFIGURATION PROTOCOL

DHCP is an application and an application-layer protocol that together enable administrators to dynamically allocate IP addresses from a pool. Computers equipped with DHCP clients automatically contact a DHCP server when they start, and the server assigns them unique addresses and all of the other configuration parameters the TCP/IP client requires.

The DHCP server provides addresses to clients on a leased basis, and after a predetermined interval, each client either renews its address or releases it back to the server for reallocation. DHCP not only automates the address assignment process; it also keeps track of the addresses it assigns, preventing address duplication on the network.

AUTOMATIC PRIVATE IP ADDRESSING

Automatic Private IP Addressing (APIPA) is the name assigned by Microsoft to a DHCP failover mechanism used by all of the current Microsoft Windows operating systems. On Windows computers, the DHCP client is enabled by default. If, after several attempts, a system fails to locate a DHCP server on the network, APIPA takes over and automatically assigns an address on the 169.254.0.0/16 network to the computer.

For a small network that consists of only a single local area network (LAN), APIPA is a simple and effective alternative to installing a DHCP server. However, for installations consisting of multiple LANs, with routers connecting them, administrators must take more positive control over the IP address assignment process. This usually means deploying one or more DHCP servers in some form.