Introduction
Method
Questions
Writeup of the lab

Introduction

The object of today's laboratory work is to examine the operation of Dynamic Host Configuration Protocol (DHCP). The function of DHCP is to obtain local configuration parameters without user intervention and incorporate those parameters into its own configuration.

Follow the instructions below and use a pen and paper to keep a record of your responses to the questions.

This work will be assessed informally during the lab period and formally at the end of the course.

Method

1. Use a suitable search engine e.g. Google to find RFC 2131. (Tip: use inverted commas around your search string to make your search more specific, i.e. enter into the search field    "RFC 2131"   )
2. Examine this document to discover key features of DHCP.

3. Answer the questions given below in your own words using a pen and paper. This means NO CUT & PASTE

4. Use the answers to your questions to help you when you write up this lab.
   

Questions
Part 1

1. How many DHCP servers are required for each subnet in your organisation? (Section 1.6 - Design Goals)
2. Make a table of the messages that may be sent by either the DHCP client or server. Make brief notes concerning the use of the message. (Section 3.1 Client-server interaction - allocating a network address)
   
3. Draw a timeline diagram of the messages exchanged between DHCP client and servers when allocating a new network address. Choose the option Server Selected. (Section 3.1 Client-server interaction - allocating a network address)
4. Which transport protocol does DHCP employ? (Section 4.1)
5. Give one reason why you think this protocol is used by DHCP over the other available option(s).
   
6. What are the numbers of the client and server ports used by DHCP? (Section 4.1)
7. Which type of address is sent by the client to the DHCP server at the beginning of the configuration process?
8. Which type of address is supplied by the DHCP server to the requesting client?
   
9. If a client no longer requires its assigned network address, describe the process that takes place between the client and DHCP server.
10. Describe TWO instances when a client should make use of DHCP  (section 3.7)
    

The object of the lab is to configure the network servers such that each PC gains an IP address via DHCP and then is able to download a webpage from the Web Server that is situated on another network.

Roll your mouse pointer over the 4 PCs to verify that they have no addressing information already.

Your PCs have browser windows and you will need to enter the address www.ens.com into the browser.

You can access the browser by clicking on a PC then selecting the Desktop tab and then select Web Browser as below.
 


Enter the address www.ens.com into the browser and click Go.

What happens?

You will need to setup the servers so that the 4 PCs are able to communicate across the network. You do not need to change any of the settings on the router or either of the switches.

You will need the following addresses to setup the servers

DHCP server IP address 192.168.0.2
Web Server IP address 192.168.100.3
DNS Server IP address 192.168.100.2

Firstly setup the DHCP server by clicking on the server in the Packet Tracer window and select the Config tab then select INTERFACE, FastEthernet.

Enter the IP address for the DHCP server as above.
 

Now setup the DHCP server so that it has the information needed to supply the PCs with their IP details.

Select the

PC DHCP client setup

Go to each PC and roll your mouse over each. Do they have addressing details? If not, why not?

You will need to turn their DHCP client on for each PC. Click on each PC and select the Desktop tab.
Select the IP Configuration tab and change the method of obtaining an IP address to DHCP from Static.
You should receive an IP address, Subnet Mask, Default Gateway and DNS Server address as below.

Now access the web browser by clicking on a PC then selecting the Desktop tab and then select Web Browser as below.
 


Enter the address www.ens.com into the browser and click Go.

What happens this time? Why can you not access the web server?

its Ethernet interface details via the appropriate tab  and its Default Gateway entered via the Global Settings tab.

Return to one of the PCs and via its Command Prompt try to ping the web server 192.168.100.3

This should be successful.

Setup the DNS Server

The DNS server should be set up now to map the canonical name to its IP address.

Click on the DNS server's Config tab and SERVICES, DNS.



Select A-Record. The A-record specifies the IP address to which the user would be sent for each domain or subdomain.

Enter the domain name www.ens.com and the IP address 192.168.100.3 and click Add.

This will map the URL to the IP address on the DNS server.

Now return to a PC and use the browser to access www.ens.com

What do you see in the browser?

If this is successful, save your packet tracer file.

What happens if you omit 'www' when you put the URL into the browser? Why do you think this happens?

Solution:

Enter the DNS tab of the DNS server. Select CNAME. Ensure www.ens.com appears in the Name field then type ens.com into the Host Name field.

You should use a CNAME record whenever you want associate a new subdomain to an already existing A record; i.e. you can make "www.ens.com" to "ens.com", which should already have been mapped to an IP with an A-record.

This allows you to have as many subdomains as you wish without having to specify the IP for every record. Use a CNAME if you have more services pointing to the same IP. This way you will have to update only one record in the convenience of a change of IP address¹.

Writeup of the lab

Keep a record of this work in your log book. Show it to your lab demonstrator before you leave. You will need to submit this work for marking.

© MMClements  Last updated : 16/11/2009 13:21