Network Access

In a Nutshell - CIW Course Section 3, Part A1, Chapter 3

Network Interface Card (NIC)

In order to connect a computer to a network it must be fitted with a network interface card (NIC). The NIC may be an expansion card or it may be an integrated part of the motherboard. It is not unusual for a server to have more than one network card as this helps spread the amount of data being carried.

Each network card requires a software device driver to manage the transfer of data to and from the network card and the computer.

Installing this device driver on a Microsoft Windows system is fairly easy as all current versions support plug and play. Adding a device driver to a Linux system may involve adding a module or it may need a kernel rebuild. The latter is more efficient but will require a system reboot.

Configuring TCP/IP Properties in Windows 2000

TCP/IP properties can be configured dynamically with DHCP, but this paragraph discusses the manual configuration.

Begin by right-clicking on "My Network Places" from the desktop and selecting "Properties" or double-clicking "Network Connections" from the control panel. Then right-click on the icon for the network connection you wish to configure and select "Properties". This will display the "Connection Properties" Dialog Box.

Select "Internet Protocol (TCP/IP)" and click the "Properties" button which will display the "Internet Protocol (TCP/IP) Properties" dialog.

If your PC is on a corporate network, then the information you will require to enter should be supplied by your network administrator. The "IP address" is the address of this network card, in most cases it is the address of this PC. The "Subnet mask" is a binary pattern that is matched with the IP Address to turn part of the Host ID address field into a field for subnets. In Windows 2000 this will default to a suitable value when you tab to the field.

The "Default gateway", in most cases, is the address of the device through which you access the Internet. This may be a separate firewall server or a DSL modem/router.

The "Preferred DNS server" is the first server this PC will contact when trying to resolve domain names. In the example above, it is a DNS Server on the local network. The "Alternate DNS server" is the address of the second DNS Server to contact should the first fail to resolve the name. In the example, this is the address of a server on the Internet, with my ISP in this instance.

Troubleshooting Utilities

The netstat utility displays current protocol statistics and allows you to determine the connection to and from a server.

ping is an oft-used utility to test basic network connectivity. It sends a request to a remote server and if the IP address is active it send a response. NOTE: Firewall servers are often configure not to respond to ping requests.

tracert is a powerful diagnostic tool that I often use with VPN (Virtual Private Network) connections. Any connection from your machine to another on the Internet is likely to traverse many routers on it's way, tracert displays all these connection points or hops. This can be very useful when a connection fails as it enables you to determine how far it got. traceroute is the equivalent utility on Unix systems.

ipconfig, by default, displays the IP configuration information for each installed network card. There are a number of options for this utility and typing ipconfig /? at the command line will display these options.

winipcfg is an equivalent utility to ipconfig in the Windows 95, 98 and Me versions of the Windows operating systems. This is not a command line utility, it is a GUI.

ifconfig is a Unix utility that is similar to the Windows ipconfig.

Dynamic Addressing

Dynamic Host Configuration Protocol (DHCP) allows the dynamic assignation of IP Addresses. This allows an administrator to control the issue of IP addresses from a central point. It further ensures that every client system has a unique address and the correct DNS and gateway settings. Each address is supplied on a lease basis, that is; each address is valid for a set period only, after which time the client must request a new address.

The client requiring an IP address cannot communicate using TCP/IP until it has a valid IP address, so the DHCP communications use UDP.