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CCIE Security Exam Certification Guide by Henry Benjamin

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Domain Name System

This section covers Domain Name System (DNS) and sample configurations used on Cisco IOS routers.

DNS's primary use is to manage Internet names across the World Wide Web. For users or clients to use names instead of 32-bit IP addresses, the TCP/IP model designers developed DNS to translate names into IP addresses.

DNS uses TCP and UDP port number 53.

In a large IP environment, network users need an easier way to connect to hosts without having to remember 32-bit IP addresses—that's where DNS comes into play. DNS provides a service that allows users to use a host's name in place of an IP Address to connect to hosts. When DNS services are running, the host's name is used to request its IP address from a DNS server. The DNS server ...

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