Homework 8

Assignment Overview

In this assignment, you will explore the various tools that an end user can use to discover what is happening in the network. You will experiment with the following five tools:

  • arp
  • traceroute
  • netstat
  • nslookup
  • whois

Assignment Details

All of these tools should be available on any machine running a UNIX-based operating system--including the machines in CSIL. You will want to make extensive use of the man pages for each command.

A. arp

  1. What is the arp table? Why does your machine need this table?
  2. What is the arp table for your machine? Provide a print out of your local machine's arp table.
  3. If you try to add or delete an entry to the arp table what happens? Why is this the case?
  4. Without being a superuser, how can you affect (either add, delete, or change) entries in the arp table? Use a mechanism to add at least one new host to the arp table and include a printout that is different from Q1.2.
  5. How long do entries stay cached in the arp table? Describe a trail-and-error method to discover the timeout value.
B. traceroute

  1. Explain in detail how traceroute works.
  2. Perform a traceroute from your machine to mail.mvnu.edu. Include a copy of the output and explain what happened including a description of what each of the fields means.
  3. What happens if you traceroute to a non-existent machine? Include a copy of the traceroute. How do you know the machine that you traced to was 1 non-existent instead of just down or not responding? (NOTE: This question is actually quite hard and requires some special thought.)
C. netstat

  1. What is netstat and what is it used for?
  2. What parameters should you use to show all the TCP connections established? Include a printout of this list.
  3. What does netstat -r show? What is noteworthy about the output?
  4. netstat can be used to display network interface status. What option of netstat does that? By using netstat, figure out the number of interfaces on your machine. In the output you will find an interface named lo0 as a loopback interface. Can you say anything about this interface, about its function?
D. nslookup

  1. What is the IP address for the machine cs.mvnu.edu?
  2. What local machine is this information coming from? Why is it coming from this machine?
  3. Here is the problem: I want to find the IP address of where my email to somebody@aol.com goes. What you really need to do is find the ``mail 1 1 exchanger'' for aol.com. There is an option in nslookup that tells you what the mail exchanger is for aol.com. Figure out the exact syntax of the format of this command, and execute it. Now what is the IP address of where my email to AOL goes?
5. whois

HINT: You will need to use a different server than the default whois server. One to try is: whois.arin.net.

HINT: Getting whois.arin.net to return information is a challenge. Make sure you try all combinations of the network name, the host address, and the network address.

  1. What class of IP address is the cs server (cs.mvnu.edu)? What is the network portion of the server's IP address? Who is the coordinator for this network?
  2. Who is the coordinator for the network that www.mvnu.edu is on?
  3. Like the AOL example, I have another friend I send email to at MSN. Her email address is something@email.msn.com. What can you say about the coordinator for the MSN email network, i.e. contact info, etc? Include information about the steps you took and the results of the queries you made to figure out this information.
Topic revision: r2 - 2013-11-10 - JimSkon
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