Section 3.2: IP Addressing

3.2.1 Configuring automatic IP Addressing

In Windows XP Professional client computer can obtain automatically an IP address from a DHCP server or through Automatic Private IP Addressing.

IP Address

An IP address is a logical 32-bit address that identifies a TCP/IP host. Each network adapter card in a computer running TCP/IP must have a unique IP address, which has two parts: a network ID that identifies all hosts on the same physical network, and a host ID that identifies a host on the network. An IP Address of indicates that the network ID is 192.168.1, and that the host ID is 66.

Subnet Mask

Subnet mask is used to subnets that divide a large network into multiple physical networks connected with routers. A subnet mask blocks out part of the IP address so that TCP/IP can distinguish the network ID from the host ID. When TCP/IP hosts try to communicate, the subnet mask determines whether the destination host is on a local or remote network. To communicate on a network, the computers must have the same subnet mask.

Default Gateway

The default gateway is a device on a local network that stores network IDs of other networks in the enterprise or Internet. To communicate with a host on another network you must configure an IP address for the default gateway. TCP/IP sends packets for remote networks to the default gateway, which forwards the packets to other gateways until the packet is delivered to a gateway connected to the specified destination. DHCP Addressing

If the network has a server running the Dynamic Host Configuration Protocol (DHCP Service, it can automatically assign TCP/IP configuration information to the client computers if the client computers are configured as DHCP clients. You can then configure any client running Windows XP Professional, Windows 2000, Windows 95, and Windows 98 to obtain TCP/IP configuration information automatically from the DHCP Service. This can simplify administration and ensure correct configuration information. Automatic Private IP Addressing

Windows XP Professional supports a new mechanism for automatic address assignment of IP addresses for simple LAN-based network configurations called Automatic Private IP Addressing (APIPA). This mechanism is an extension of dynamic IP addressing and enables the configuration of IP addresses without using static IP address assignment or installing the DHCP Service.

On a computer running Windows XP Professional you must configure a network LAN adapter for TCP/IP and click Obtain an IP Address Automatically in the Internet Protocol (TCP/IP) Properties dialog box for the Automatic Private IP Addressing feature to function properly.

APIPA can be used to set up IP configuration to allow network communication on a single subnet and is also used when the client computer cannot contact the DHCP server for IP address configuration. APIPA uses an addressing range from through and a subnet mask of

3.2.2: Configuring Static IP Addressing

By default, client computers running Windows XP Professional, Windows 2000, Windows 95, or Windows 98 obtain their IP configuration information automatically from the DHCP Service. However you should assign a static IP address to certain network computers, such as the computer running the DHCP Service. If the DHCP Service is not available, you can configure TCP/IP to use a static IP address. For each network adapter card that uses TCP/IP in a computer, you can configure an IP address, subnet mask, and default gateway

3.2.3: Testing TCP/IP Configuration

After you configure the TCP/IP configuration, you must restart the computer, and use the ipconfig and ping command-prompt utilities to test the configuration and connections to other TCP/IP hosts and networks and to ensure that TCP/IP is functioning properly.

  • Ipconfig can be used to verify the TCP/IP configuration parameters on a host. This can be used to determine whether the configuration is initialized, or whether a duplicate IP address exists on the network. Use the ipconfig command with the /all switch to verify configuration information.
  • Ping can be used to test the computer's connectivity after you have verified the TCP/IP configuration. The ping utility is a diagnostic tool that you can use to test TCP/IP configurations and diagnose connection failures. You can use the ping utility to determine whether a particular TCP/IP host is available and functional.
  • Tracert. Traces the route that a packet takes to a destination. The tracert command displays a list of IP routers that are used to deliver packets from your computer to the destination, and the amount of time that the packet remained at each hop or the destination between two routers. If the packets cannot be delivered to the destination, you can use the tracert command to identify the last router that successfully forwarded the packets.
  • Nslookup Nslookup is a command-line utility that you can use to query and troubleshoot your DNS installation. Name resolution errors can result if:

    • DNS client entries are not configured correctly.
    • DNS server is not running.
    • There is a problem with network connectivity.
    At a command prompt, type nslookup to view the host name and IP address of the DNS server that is configured for the local computer.