HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> Emulab Network Lab

Addressing and Routing on Emulab

Due date

Check the course calendar for the due date.

Introduction

In this lab you will create an emulated network using the Emulab environment.  Using an emulator allows one to prototype network architectures and performance. In this lab, you will investigate addressing and routing. You will use this network in future labs, so make sure that you document your network

Goals

Acknowledgments

This lab is based on experiment 15 from Hands-On Networking with Internet Technologies by Douglas Comer (2nd edition, 2005). Janet Davis did the first conversion to Emulab

References

RFCs 950, 4632

Logistics

This is a team project in that each team will have their own network developed within Emulab.  It is expected that you will talk to other students, faculty, etc., about the project.

You have plenty of time couple to complete this assignment if you start early to allow time to acquire the necessary Emulab resources.

Preparation

You should already have a login for the Emulab project. Please terminate your old experiments if you are done with them.

Assignment

Part A: Subnetting

  1. Create an \textit{ns}file to configure the following network. Don't start your experiment just yet.

    Your network will include four LANs.  LAN A is connected to LAN B by a router and to LAN C by another router.  LAN B is connected to LAN C by another router and LAN C is connected to LAN D by another router.  In addition to the routers, each LAN has two other hosts.

  2. With pencil and paper, plan the addressing scheme for your network.

    1. Use the IP address 192.168.0.0 as the overall network address.

    2. Use the third octet to assign a unique subnet address to each of the four LANs.

    3. In assigning each router interface, determine a 'standard' method of assigning router IP addresses on each subnet.  What approach is used on the CS Network? (Hint: Use netstat -r -n and look at the default route.)

  3. Modify your ns file to specify an address for each interface using the command tb-set-ip-lan, which is documented here.

  4. Finally, run your ns file as a new experiment! When you are successful, paste your ns file and the visualization of the resulting network into your lab notebook.

  5. Use netstat -r -n, ping, and traceroute to check out your network. (Don't go overboard; checking a few paths should suffice.) Record these exchanges using script and paste them into your notebook.

Part B: Enabling RIP

  1. Enable routing using RIP as follows.
    1. Disable static routing by commenting out the appropriate line in the ns.
    2. For each router, add a line of the following form to your ns. file:
      tb-set-node-startcmd $routerName "/proj/Nelson/router-startup"
    3. For each host, add a line of the following form to your ns. file:
      tb-set-node-startcmd $nodeName "/proj/Nelson/host-startup <net-address> <netmask> <router-name>"

      net-address should be the address of your network, 192.168.0.0.  Normally this would be a default route, but you need to be able to ssh to your nodes over the Internet!

    The result of adding these lines is to run scripts located in the /proj/Nelson directory upon startup of each node.  Janet wrote these scripts, and we will look at them later. LET ME KNOW IF YOU RUN INTO PROBLEMS WITH THIS!

    Note that the script files assume your routers are named routerA, routerB, routerC, and routerD,  If you've given them different names, you should make your own copies of the files router-startup, host-startup, and gated.conf in your Emulab home directory, /users/<username>. 

  2. Restart your experiment.

  3. Use netstat -r -n, ping, and traceroute to check out your network.  Record these exchanges using script and paste them into your notebook.

  4. On one of the nodes, examine the contents of the /proj/Nelson directory. Answer the following questions.
    1. What does the router-startup script do?
    2. What does the host-startup script do?
    3. What seems to be the purpose of the gated.conf file?
Notes:

Part C: Experiments with RIP

  1. Read about Emulab's event interface in the advanced tutorial. 

  2. Take a router down by executing a following command of the following form: tevc -e proj/exp now routerAB down

  3. Use netstat -r -n, ping, and traceroute to see how routes have changed as a result of this change in network connectivity. Record these exchanges using script and paste them into your notebook.

  4. Bring the router back up and see whether the original routes are restored.

Part D: Traffic Generation

  1. For each of your nodes, find a way to generate application level traffic, e.g., ftp, telnet, dns, etc. Post whatever you find to Piazza so that everyone can easily generate traffic.
  2. There are probably traffic generators in Emulab, but I am not sure how to access them, e.g., there is an NS tool known as Agent/CBR.
  3. There are probably traffic generators for the particular OSs run on your notes, e.g., http://www.postel.org/tg/tg.html..
  4. From others: On the Emulab graphical network creation page: https://www.emulab.net/clientui.php3 you can set up traffic generation by selecting two nodes and pressing the plus button under traffic generators.
  5. When you find something that works:

Part E: CIDR

  1. Consider the CIDR block 192.186.0.0/13.  Use 9 additional bits (beyond the /13 prefix) for subnet addressing, and assign a unique subnet address to each of the 5 networks in your intranet.  Write down the addresses in CIDR notation.

  2. Assign an IP address to each router interface, and configure each router with an address and mask for each of its interfaces.

  3. Configure the routing table in each router with next-hop information for each of the five possible destination networks. (Do not enable automatic routing update protocols).

  4. Assign each host an IP address, and configure each host to know its address.

  5. Use ping and traceroute to checkout your network.  Record these exchanges using script.

WHEN YOU ARE DONE, PLEASE SWAP OUT YOUR EXPERIMENT SO THAT OTHERS CAN USE YOUR NODES!

Assessment

It is obvious that each team will have different answers. If you comment your actions well, we will be able to understand what each team did.

Advice

Emulab is a shared resource used by many schools and research labs.   Thus, you might have to schedule your time to ensure that you can get particular resources. That is especially true for this assignment, which will require a total of 12 nodes!

Traffic Generation Issues

Lab Notebook

Include your nsfile, a visualization of your network, answers to any questions embedded in the lab exercises, and appropriate script sessions.

In this case submit your lab report as emulabintranetworking.pdf or emulabintranetworking.txt.

Discussion Questions

  1. Use whois to find out who owns the 192.168.0.0 class B address block. Why do you think you were asked you to use this as the address for your network?

  2. Why do you think we did not have you change the default route for your nodes? (Hint: Look back at the default route in the output you got from netstat -r -n. What was the address of the default router?)

  3. P&D exercise 4.26

  4. How long did you spend on this lab? How did you spend your time?

WHEN YOU ARE DONE, PLEASE SWAP OUT YOUR EXPERIMENT SO THAT OTHERS CAN USE YOUR NODES!

Mike Erlinger

Last Modified Thursday, 03-Apr-2014 12:23:05 PDT