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CompTIA A+ Certification All-in-One Exam Guide

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Figure 19-3 Default gateway

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 designations. The system they came up

with is called the Domain Name Service (DNS). Special computers, called

DNS servers, keep databases of IP addresses and their corresponding names.

For example, let’s say a machine with the IP address 209.34.45.163 hosts a

Web site and we want it to be known as www.totalsem.com. When we set up

the Web site, we would pay for a DNS server to register the DNS name

www.totalsem.com to the IP address 209.34.45.163. So instead of typing

“http://209.34.45.163” to access the Web page, you can type

“www.totalsem.com.” Your system will then query the DNS server to get

www.totalsem.com’s IP address and use that to find the right machine.

Unless you want to type in IP addresses all the time, you’ll need to use DNS

servers (see Figure 19-4).

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