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:

1. arp
2. ifconfig
   
3. traceroute
4. netstat
5. nslookup
6. tracenet --- optional

Assignment Details
These tools (except for tracenet) should be available on machines running a UNIX-based operating system. Some of these tools may not perform as expected on netXX.utdallas.edu machines as these machines are configured in a way to avoid sending unnecessary traffic to outside world. In those cases, try running the tools on some other CS or UTD UNIX machines (e.g., cs1.utdallas.edu or cs2.utdallas.edu).  The absolute paths for each of the tool is given in the parenthesis below.

During the assignment, you will need to consult the "man pages" of these tools and will want to do some search on the web.

arp   (/usr/sbin/arp)

1. Learn what ARP protocol is and what it is used for. 
2. What is the arp table? Why does your machine need this table?
3. What happens when you try to add/delete an entry into the arp table on your machine? 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 Part 2 above.

ifconfig  (/usr/sbin/ifconfig)

1. Run "ifconfig -a" on your local machine. Capture the output and identify and explain as much of what is printed as you can. 
2. What is the command to determine whether the network interface is controlled by DHCP or not?

traceroute (/usr/sbin/traceroute)

1. Explain in detail how traceroute works.
2. Perform a traceroute from your machine to www.metu.edu.tr . 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 non-existent instead of just down or not responding? (NOTE: This question is actually tricky and requires some special thought.)

netstat  (/usr/bin/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?

nslookup (/usr/sbin/nslookup)

1. What is the IP address for the machine morticia.cc.gatech.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 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?

tracenet -- this is optional and will not be graded (available at http://itom.utdallas.edu/tracenet_download.html)

Tracenet is a new network diagnostic tool that we have recently developed here at UTD. We would like you to download it at the above URL and install it on your Linux machine. The tool requires root privileges and therefore you cannot use it on UTD Linux servers as you would not have root access to them. If you have a PC running Linux, you can install it on your system and use it. Alternatively, you can create a virtual machine on your Windows PC and install Linux and then install tracenet and use it there. Basically, we would like your feedback about the tool and things that you can do with it. Here are some questions to suggest what we want to learn from you:

1. What is the difference between traceroute and tracenet returned information? How can you make use of this information for network diagnosis, etc.
2. What might be a context that you would benefit from tracenet other than network diagnosis?
3. How would you improve on the user interface, amount of provided information, intuitiveness of the tool for a novice user, etc.

Turn In: A soft copy of the assignment including all the related outputs of the programs thru eLearning.