A+ Certification / Beginners

The HOSTS file

Very similar to the idea of using an LMHOSTS file for NetBIOS name resolution (see "The LMHOSTS file" section, earlier in the tutorial), you can use a text file, called the HOSTS file, for host name resolution. The HOSTS file is located in the %systemroot%\system32\drivers\etc folder on Windows 2000, XP, and Windows Server 2003 systems.

The configuration of the HOSTS file is similar to the configuration of the LMHOSTS file; you simply create two columns - one for the FQDN and the other for the IP address of the system. You separate these columns with a Tab keystroke.


Be aware that another layer of resolution needs to happen after your client has the IP address of the system it wants to communicate with. You know that there is a different database for FQDN resolution and computer name resolution - the DNS database stores fully qualified domain names and their IP addresses, while the WINS database stores computer names and associated IP addresses. Once the name is converted to the IP address, the IP address then must be resolved to the hardware address that is burned into the network card. This hardware address that is assigned to each network card is known as the Media Access Control(MAC) address. This means that there has to be a process that converts the IP address to the MAC address - a process known as Address Resolution Protocol, or ARP. ARP is an address resolution protocol that converts the IP address to the physical address assigned to the network card.

ARP is a broadcast, or a yell, out on the wire for a particular address. Looking at an example of Computer A trying to send information to Computer B, after Computer A has the IP address of Computer B (, Computer A yells at the top of its lungs, "Hey,! What is your network card's MAC address?" This yell runs along the network and eventually reaches Computer B, which responds with its MAC address. After Computer A has the MAC address of Computer B, it can then send the data to Computer B.

It is important to note that ARP messages are broadcast messages, and broadcast messages do not pass through routers. This doesn't cause a problem because when you want to communicate with a system on a different network, your system sends the data to the default gateway, or router, and then the router sends the data off the network by ARPing the router on the destination network. In this example, your system communicates with the router, so it would ARP the router, not the destination system!

Planning TCP/IP settings

Determine what TCP/IP services are required to fit the scenario below. The answer follows the scenario.

Scenario: You are responsible for implementing a TCP/IP-based network across all of the office locations in your region. What TCP/IP options will you set, and which additional TCP/IP-based services will you implement?

Answer: You may want to set a DNS server to store the FQDN and IP addresses of the different servers on your network. You may also want to run a WINS server for computer name resolution because it is a WAN environment.

After you set up the DNS and WINS servers, you will install a DHCP for each network segment so that you can hand out IP address, subnet mask, and default gateway information to the clients on the network. You will also hand out the IP address of the DNS server and the WINS server through DHCP so that the clients are fully configured.

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