Observing DNS Name Resolution

Lab 6.2.1 Observing DNS Name Resolution

Objectives

  • Observe the conversion of a URL to an IP address.
  • Observe DNS lookup using the nslookup command.

Background / Preparation

Domain Name System(DNS) is called when you type a Uniform Resource Locator(URL), such as , into a web browser.

The first part of the URL describes which protocol is being used:

  • HTTP (Hypertext Transfer Protocol)
  • HTTPS (Hypertext Transfer Protocol over Secure Socket Layer)
  • FTP (File Transfer Protocol)

DNS translates the domain name (like to an IP address.

Step 1: Observe DNS conversion

  1. Start the command prompt window.
  2. Type ping . The computer needs to translate into an IP address. Ping is a type of ICMP packet.
  3. The first line shows converted to an IP address by DNS.

  1. Which IP address is shown on your screen? ______
  2. Is it the same as the one shown in the figure? ______Why do you think this occurred? ______
  3. Give other examples (besides the ping command) in which the computer uses DNS.

______

Step 2: Verify DNSoperation using the nslookup command

  1. At the command prompt, type the nslookup command.
  1. What is the default DNS server being used? ______
  2. The command prompt changed. This is the NSLOOKUP prompt. From this prompt, you can enter commands related to DNS.
  3. Type ? to see a list of all the available commands.
  4. Write three commands that you can use with NSLOOKUP. ______

______

______

  1. At the NSLOOKUPprompt, type .
  2. What is the translated IP address? ______
  3. Is it the same as the IP address shown with the ping command? ______
  4. Type the IP address of the Cisco web server that you just found. You will get the domain name of the IP address.

Find an IP address of ______

Step 3: Identify mail servers using the nslookup command

  1. At the prompt, type set type=mx to have NSLOOKUP identify mail servers.
  1. At the prompt, type .
  2. What is the primary name server, the responsible mail address, and the default Time to Live(TTL)? ______

______

  1. At the prompt, type exit to return to the regular command prompt.
  2. At the prompt, type ipconfig /all.
  3. Write the IP addresses of all the DNS servers that your school uses.

______

  1. Type exit to close the command prompt window.

Step 4: Reflection

  1. If your school did not have a DNS server, what effect would this have on your use of the Internet?

______

______

______

  1. Some companies do not dedicate a single server for DNS. Instead, the DNS server provides other functions as well. Which functions do you think can be included on a DNS server? Use the ipconfig/all command to help you.

______

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