Core 5.1
Lab #2: URLs, IP addresses, DNS names, tracert

"Show and Tell"

Do this lab using Internet Explorer! (The visual traceroute doesn't work under Netscape, and the error message for invalid or unreachable hosts are better under Explorer.)
  1. You can't judge a domain by its name

    1. Open a Web browser and go to http://www.gwbush.com. Compare the site with http://www.georgebush.com.
    2. Yahoo is pretty smart about it -- check out http://www.yahop.com and http://www.yahoo.org

  2. DNS names <-> IP addresses

    1. We will use a utility called ping to obtain IP addresses corresponding to DNS names.

      You will need to get to a DOS prompt to run ping. Click on the Start button, then on Run... A window will pup up, with a text area that might be filled in already. Delete whatever is there and type in command. A DOS window should come up.

      To use ping, type ping www.whatever.com to ping that computer.

      In Room 130aNE, because of the proxy server, ping will respond with an error message. Nevertheless, it will still translate DNS names into IP addresses.

      Use ping to find the IP addresses for these DNS names:

      1. www.cuny.edu
      2. www.yahoo.com

    2. What happens if you type in a DNS name incorrectly? Try linking to http://www.brooklyn.cuny.e or http://www.brklyn.cuny.edu
      Try to ping those DNS names - try ping www.brooklyn.cuny.e and ping www.brklyn.cuny.edu

    3. What happens if you type in an IP address directly, instead of a DNS name? Try linking to http://146.245.100.20.

    4. What if you type the IP address in incorrectly? Try linking to http://146.245.100.2.
      Now try linking to http://146.245.245.2. Note the different error messages.
      If you are not in Room 130aNE, you can try to ping them with ping 146.245.100.2 and ping 146.245.245.2

    3. The following section will not work in Room 130aNE because of the proxy server.
  3. Tracing a route through the Internet

    We will use tracert to trace the route from your machine to other computers on the Internet. To use tracert, you will also need to use the DOS window. To use tracert to a site called www.whatever.com, type tracert www.whatever.com.

    1. Use tracert to track a route to these sites.
      1. www.yahoo.com
      2. www.cuny.edu
      3. home.netscape.com

    2. The next few sites are foreign - can you tell which countries they are in?
      1. www.webspot.com.au
      2. www.insee.fr

    In each case, note the IP address of the destination, and the number of hops it took to reach the destination. Can you say anything about the setup of the Brooklyn College LAN? Can you tell how messages get routed out of Brooklyn College?

  4. Visualizing a route

    1. Open this page in another window (right-click on it, then select "Open in New Window").  Wait for the table and map to appear in the middle of the page.  This page provides a visualization tool for tracert (and in some cases a little more information). First, just click on the "Start Trace" button near the top of the page.  Then click the "Show Details" box to the right of the "Start Trace" button. You should be able to answer the following questions:

      1. What is your computer's IP address?
      2. How many routers does information travel through between your computer and the website in Dulles?
      3. Which companies own those routers?  (You can adjust the column separators with your mouse to see the complete "Node Names"; look at the last couple portions of the names; or look at the "Network" column.)

    2. Go here to try using the same tool from a website in Australia.  Try looking up www.mta.info.  Where is the first router encountered in the USA?