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NET463
Lab #1 – DHCP and NAT
ASSIGNMENT DOCUMENT
Must be done on Packet Tracer
Version 2 (revised Q9 in NAT section)
Lab Scenario:
In this lab, you will be configuring routers and a DHCP server to enable DHCP IP address assignment and
Network Address Translation (NAT) using Packet Tracer. The network diagram of Figure 1 illustrates a LAN
network connected to a WAN. In this network, a WAN DHCP server provides the dynamic IP address
assignment to the LAN hosts (Hosts 1,2 and 3). To enable DHCP IP address assignment in this network,
Router R1 must be configured as a DHCP relay agent. As discussed in lecture, a DHCP relay agent
forwards DHCP packets between clients and servers when they are not on the same physical subnet. Relay
agent forwarding is distinct from the normal forwarding of an IP router, where IP datagrams are switched
between networks somewhat transparently. By contrast, relay agents receive DHCP messages and then
generate a new DHCP message to send out on another interface. The relay agent sets the gateway address
(giaddr field of the DHCP packet) and, if configured, adds the relay agent information option.
In addition, this lab will demonstrate how NAT translates IP addresses. As discussed in lecture, NAT
translates non-routable private, internal addresses into routable, public addresses. NAT has an added
benefit of providing a degree of privacy and security to a network because it hides internal IP addresses
from outside networks. In this Lab, you will configure NAT overload. To demonstrate this capability, Router
R1 will be configured to perform NAT translation.
DHCP IP Address
Assignment
192.10.1.0/24
Up to 50 users
DHCP Server
R1
NAT Router
DHCP Relay Agent
Host1
Fa0/0
Host2
Fa0/1
Fa0/0
Fa1/0
192.10.1.1
Fa0/0
192.168.20.0/24
Host3
200.10.1.2
Fa0/0
200.10.1.0/24
200.10.1.1
Fa0/1
168.10.1.0/30
Fa0/0
Switch S1
R2
WAN Edge
Router
Fa0/0
200.10.1.3
Fa0/0
Host4
192.168.20.254
Internal Web Server
Figure 1: Lab #1 Network Diagram
Learning Objectives
•
•
•
•
•
Configure an ACL to permit NAT
Configure dynamic NAT with Overload
Configure a router as a DHCP relay agent
Configure a DHCP server
Test connectivity and debug using pings
IP Address Requirements:
Lab #1 Assignment
NET 463
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Use the IP address assignments show in Lab #1 Network Diagram. If an interface in the diagram does not
have a specific IP address assigned to it, then assign one yourself but ensuring that the IP address
assignment is within the subnet.
Lab Environment:
You MUST configure and test this lab using a network simulator such as Cisco’s Packet Tracer. Unlike all of
the other labs in this class, there is no DLPOD/POD available to conduct this lab. Use the Cisco 2811
router. Also, you need to insert the NM-1FE-TX expansion card to the router to enable three fast Ethernet
interfaces to the device.
Lab Procedure: DHCP Address Assignment
Follow these steps to complete this portion of the lab:
1.
Configure all IP interfaces on all devices using addresses from Table #1 above and subnet masks
according to Table #1: Subnet Design that you filled out in Lab #1 Answers file. Remember to do
a no shutdown on each router interface. Set default gateway values on Hosts/Servers to the
local router interface.
2.
On each router, configure routing protocol RIPv2. To configure RIPv2, enter the following
commands to each router:
router rip
version 2
After configured for rip routing, advertise the 1) serial link subnet that connects the two routers
and 2) the 200.10.1.0 subnet by using network commands while in router configuration mode.
As an example, for router R2, you should enter two network commands:
network 200.10.1.0
network 168.10.1.0
3.
Configure router R1 to be a DHCP relay agent by executing the command ip helper-address
200.10.1.2 on the Fa0/1 interface.
4.
Configure the DHCP server to dynamically assign IP addresses to hosts in the subnet
192.10.1.0/24
5.
Configure the DHCP server to dynamically assign the default gateway IP address to 192.10.1.1 for
each of the hosts. The 192.10.1.1 IP address should be assigned to the router R1 Fa0/1
interface). Allow IP assignment of up to 50 users (max). Also name this pool “NET463_W2021”.
6.
Now proceed to the questions related to the DHCP section of the the Lab Report by executing
the commands specified and pasting all screenshots requested.
Lab Procedure: Network Address Translation (NAT)
Follow these steps to complete this portion of the lab:
7.
Create a named standard Access Control List (ACL). To define the internal addresses that are
translated to public addresses in the NAT process, create a named standard ACL called R1NAT.
This list is used in the NAT configuration steps that follow.
R1(config)#ip access-list standard R1NAT
R1(config-std-nacl)#permit 192.10.1.0 0.0.0.255
Lab #1 Assignment
NET 463
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8.
Configure dynamic NAT to allow any host in subnet 192.10.1.0/24 to access the Internet at the
same time. Configure NAT with overload to accommodate the additional hosts. NAT overload,
also called Port Address Translation (PAT), uses port numbers to distinguish packets from
different hosts that are assigned the same public IP address.
Enter the following command to router R1 to configure the public address that is dynamically
mapped to the internal hosts.
R1(config)#ip nat inside source list R1NAT inter fa1/0 overload
9.
Configure the interfaces on R1 to apply NAT. In interface configuration mode on R1, configure
each of the interfaces using the ip nat {inside | outside} command. Because the internal
addresses are on networks connected to the Fa0/0, Fa0/1 interfaces, use the ip nat inside
command in configuring these interfaces. The Internet is connected to Fa1/0, so use the ip nat
outside command on this interface
10. Now proceed to the questions related to the NAT section of the Lab Report by executing the
commands specified and pasting all screenshots requested.
Lab #1 Assignment
NET 463
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Lab Report / Questions (100pts):
IP Address Plan
(10%) Based on the network diagram, assign a specific IP address and subnet mask to each interface and
enter it into the table below.
Table #1: IP Address Assignment
Device
R1
R1
R1
R2
R2
Internal Web
server
DHCP Server
Host4
Interface
Fa0/0
Fa0/1
Fa1/0
Fa0/0
Fa0/1
IP Address
Mask
Fa0/0
Fa0/0
Fa0/0
Lab Implementation (90%)
Once you have implemented and tested your network, answer each of questions below. Note that all
screenshots must contain only a single window, not your entire desktop. To do this on Windows,
highlight the window, type Alt-Printscreen to capture active window, then CTL-V to paste it into
document. On Mac you can use the Grab utility.
Lab Procedure: DHCP Address Assignment Questions:
1.
(20%) In the Desktop tab of each PC, click IP Configuration, and then select DHCP. The IP
configuration information should be immediately updated. Include a screenshot of the results
for Host 1, 2, and 3 and paste here.
2.
(10%) On Host #1, execute a ping to host #4. Include a screenshot of the results and paste here.
3.
(5%) On the DHCP server in the DHCP-services dialog box, include a screenshot of the results and
paste here.
4.
(5%) The Source IP address and Destination IP address of the DHCPDISCOVER message from the
client(s) prior to being assigned an IP address are:
Source IP address =
Destination IP address =
5.
(5%) What DHCP message does the Router send back to the client in the local subnet that
contains the information such as subnet mask, default gateway, IP address lease time, and
domain name server (DNS)?
Lab #1 Assignment
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DHCP message: __________
6.
(5%) What DHCP message does the Client send back to the router in the local subnet that
communicates that it accepts the offer?
DHCP message: __________
7.
(5%) What DHCP message does the Router send back to the client to acknowledge and conclude
the address assignment?
DHCP message: __________
8.
(5%) Which one of the messages above is unidirectional in the subnet?
DHCP message: __________
Lab Procedure: NAT Questions:
9.
(10%) On the inside web server, execute a ping from Host #1 to Host #4 include a screenshot of
the results and paste here.
10. (10%) You should now be able to ping from any inside host to Outside Host or the DHCP Server.
To see the effects of NAT on a specific packet, enter Simulation mode in Packet Tracer and
observe the packet that originates from a ping on Host 1. Click the colored information box
associated with that packet as it is passed from Host 1 to R1. By clicking Inbound PDU Details,
you should see that the source address is IP address that was assigned by DHCP earlier in the lab.
Include a screenshot of the results and paste here. By clicking Outbound PDU Details or R1, you
should see that the source address has been translated to the 168.10.1.1 address. Include a
screenshot of the results and paste here.
11. (5%) In Lab #1 NAT portion of the lab, was “over-loading” demonstrated (YES or NO)? If YES,
then explain how the NAT router supports “overload”. That is, how does the router translate
many private IP addresses to fewer public IP addresses?
12. (5%) Based on your above explanation, discuss why such a method presents challenges with Ping
packets and how this is generally resolved (hint: think about how Ping OSPF packets are
encapsulated, that is, are they encapsulated in UDP or TCP?).
13. (5%) On router R1, display the PAT translation table by entering the command show ip nat
translations and include a screenshot of the results and paste here.
14. (5%) For the PAT address translation portion of Lab #1, provide an IP address example for each
the following:
inside local address:
inside global address:
outside global address:
Lab #1 Assignment
NET 463
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