[cs615asa] HW 4
Jan Schaumann
jschauma at stevens.edu
Thu Mar 16 20:30:49 EDT 2017
Mark Wilson <mwilson3 at stevens.edu> wrote:
> I am having trouble accessing the class website. If anyone has the
> homework 4 assignment either printed or can access it online, can you
> take pictures of it and send it along?
Did you file a ticket with Stevens support? If nobody knows that a
problem exists, nobody can fix it.
If you have access to linux-lab, you can access all data available on
the course website from ~jschauma/public_html/615/.
For example, the attached text version was generated using this command:
links -dump ~jschauma/public_html/615/s17\-hw4.html > hw4.txt
-Jan
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|CS615A -- Aspects of System Administration - HW#4 |
| |
| HW4: tcpdump(1) DNS |
| |
| Objective |
| |
| The objective of this assignment is for you to learn how to use |
| tcpdump to observe and analyze network traffic. This reinforces |
| lessons from our lecture on networking and prepares you for our |
| lecture on the DNS. |
| |
| In order to be able to observe DNS traffic flowing between your host |
| and the DNS root servers as well as other DNS servers, you will need |
| to set up and configure a simple caching name server, aka a resolver. |
| |
| Note: you must use tcpdump. Graphical helper applications such as |
| "wireshark" or similar tools are explicitly prohibited. You need to be |
| able to read the flat text tcpdump output yourself and not rely on |
| other tools to highlight things for you. |
| |
| Summary |
| |
| This assignment consists of multiple parts. Please carefully read the |
| assignment in full before you begin. |
| |
| This assignment is worth 40 points. |
| |
| OS Instances |
| |
| The exercises below can be done on any OS instance you like. You will |
| need at least two OS instances, one for the DNS server and one for the |
| "client". Make sure that the firewall rules between the server and |
| client allow for all the required traffic. |
| |
| DNS server setup |
| |
| Set up a caching only DNS server (a ``resolver'') on your OS instance. |
| You may consult any online documentation available, such as this |
| document or any others you prefer. You may use bind or any other DNS |
| server software you like. The only restriction is that in the end your |
| host must be able to function as a caching DNS server. |
| |
| Set up your client host to use your newly created DNS server for host |
| lookups. |
| |
| tcpdump exercises |
| |
| Use the tcpdump utility to monitor the network traffic using the |
| following scenarios: |
| 1. on the DNS server, run the following commands: |
| |
| $ telnet www.yahoo.com 80 |
| GET / HTTP/1.1 |
| Host: www.yahoo.com |
| |
| |
| * Track down the packets in your tcpdump referring to the DNS |
| query from your DNS server to one of the root servers, then |
| to the various DNS servers before the DNS information is |
| returned to your server by one of Yahoo's authoritative DNS |
| servers. |
| * Identify the 3-way handshake that initiates the connection |
| from your DNS server to port 80 on Yahoo's webserver, the |
| packets that are being sent back and forth and finally the |
| closing of the connection. |
| |
| 2. on your client host, run the following commands: |
| |
| $ telnet www.tumblr.com 80 |
| GET / HTTP/1.0 |
| |
| |
| * On your client: Track down the packets in your tcpdump |
| referring to the DNS query from your client host to your DNS |
| server. |
| * On your DNS server: Track down the packets in your tcpdump |
| referring to the DNS query from your DNS server to one of the |
| root servers, then to the various DNS servers before the DNS |
| information is returned to your server by one of Tumblr's |
| authoritative DNS servers. |
| |
| 3. on the DNS server, perform a reverse host lookup (PTR) for a |
| record not yet in your DNS server's cache; track down in your |
| tcpdump all relevant DNS queries required to retrieve the result. |
| Clearly identify which name servers you are communicating with and |
| who operates them. |
| |
| You must submit: |
| * a plain text description, properly formatted and spell checked, of |
| how you set up your DNS server and how you configured the client |
| * the trimmed and formatted tcpdump output showing the information |
| requested above |
| * commentary on what you learned, what you found difficult, what you |
| found surprising |
| |
| Deliverables Due Date |
| |
| The due date for this assignment is 2017-03-20 16:00 EDT. |
| |
| You will submit a single tar(1) archive. The file to submit will be |
| called "$USER-hw4.tar" (where "$USER" is your username). The archive |
| will extract all files and subdirectories into a directory named |
| $USER. |
| |
| Please attach the file to an email sent from your @stevens.edu email |
| address to jschauma at stevens.edu with a subject of "[CS615] HW4". |
| |
| ------------------------------------------------------------------ |
| |
| [Course Website] |
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