CompTIA A_ Certification All-In-One Exam Guide, Seventh Edition - Michael Meyers [414]
Default Gateway A computer that wants to send data to another machine outside its LAN is not expected to know exactly how to reach every other computer on the Internet. Instead, all IP hosts know the address of at least one router to which they pass all of the data packets they need to send outside the LAN. This router is called the default gateway, which is just another way of saying “the local router” (Figure 23-28).
Domain Name Service (DNS) Knowing that users could not remember lots of IP addresses, early Internet pioneers came up with a way to correlate those numbers with more human-friendly computer designations. Special computers, called domain name service (DNS) servers, keep databases of IP addresses and their corresponding names. For example, a machine called TOTALSEMINAR1 will be listed in a DNS directory with a corresponding IP address, such as 209.34.45.163. So instead of accessing the \\209.34.45.163\FREDC share to copy a file, you can ask to see \\TOTALSEMINAR1\FREDC. Your system will then query the DNS server to get TOTALSEMINAR1’s IP address and use that to find the right machine. Unless you want to type in IP addresses all of the time, a TCP/IP networks will need at least one DNS server (Figure 23-29).
Figure 23-28 Setting a default gateway
Figure 23-29 Adding two DNS servers in Windows Vista
The Internet has regulated domain names. If you want a domain name that others can access on the Internet, you must register your domain name and pay a small yearly fee. In most cases, your ISP can handle this for you. Originally, DNS names all ended with one of the following seven domain name qualifiers, called top level domains (TLDs):
As more and more countries joined the Internet, an entire new level of domains was added to the original seven to indicate a DNS name in a particular country, such as .uk for the United Kingdom. It’s common to see DNS names such as www.bbc.co.uk or www.louvre.fr. The Internet Corporation for Assigned Names and Numbers (ICANN) announced the creation of several more new domains, including .name, .biz, .info, and others. Given the explosive growth of the Internet, these are unlikely to be the last ones! For the latest developments, check ICANN’s Web site at www.icann.org.
WINS Before Microsoft came fully on board with Internet standards such as TCP/IP, the company implemented its own type of name server: Windows Internet Name Service (WINS). WINS enables NetBIOS network names such as SERVER1 to be correlated to IP addresses, just as DNS does, except these names are Windows network names such as SERVER1, not fully qualified domain Internet names (FQDNs) such as server1.example .com. NetBIOS names must be unique and contain 15 or fewer characters, but other than that there isn’t much to it. Assuming that a WINS server exists on your network, all you have to do to set up WINS on your PC is type in the IP address for the WINS server (Figure 23-30). Networks based on Windows 2000/XP/Vista/7 don’t use WINS; they use an improved “dynamic” DNS (DDNS) that supports both Internet names and Windows names. On older networks that still need to support the occasional legacy Windows NT 4.0 server, you may need to configure WINS, but on most TCP/IP networks you can leave the WINS setting blank.
DHCP The last feature that most TCP/IP networks support is dynamic host configuration protocol (DHCP). To understand DHCP, you must first remember that every machine must be assigned an IP address, a subnet mask, a default gateway, and at least one DNS server (and maybe a WINS server). These settings can be added manually by using the TCP/IP Properties window. When you set the IP address manually, the IP address will not change and is called a static IP address (Figure 23-31).
DHCP enables you to create a pool of IP addresses