14.8.1 Packet Tracer - TCP and UDP Communications
14.8.1 Packet Tracer - TCP and UDP Communications
14.8.1 Packet Tracer - TCP and UDP Communications
Objectives
Part 1: Generate Network Traffic in Simulation Mode
Part 2: Examine the Functionality of the TCP and UDP Protocols
Background
This simulation activity is intended to provide a foundation for understanding TCP and UDP in detail. Packet
Tracer simulation mode provides you the ability to view the state of different PDUs as they travel through the
network.
Packet Tracer Simulation mode enables you to view each of the protocols and the associated PDUs. The
steps outlined below lead you through the process of requesting network services using various applications
that are available on a client PC. You will explore the functionality of the TCP and UDP protocols,
multiplexing, and the function of port numbers in determining which local application requested the data or is
sending the data. Packet Tracer will not score this activity.
Instructions
2013 - 2020 Cisco and/or its affiliates. All rights reserved. Cisco Public Page 1 of 6 www.netacad.com
Packet Tracer - TCP and UDP Communications
b. Enter the nslookup multiserver.pt.ptu command. A PDU will appear in the simulation window.
c. Minimize, but do not close, the DNS Client configuration window.
Step 6: Verify that the traffic is generated and ready for simulation.
There should now be PDU entries in the simulation panel for each of the client computers.
2013 - 2020 Cisco and/or its affiliates. All rights reserved. Cisco Public Page 2 of 6 www.netacad.com
Packet Tracer - TCP and UDP Communications
d. Click Capture/Forward until you see a PDU appear for HTTP. Note that the color of the envelope in the
topology window matches the color code for the HTTP PDU in the Simulation Panel.
Question:
Flag Place 6 5 4 3 2 1
Value URG ACK PSH RST SYN FIN
Question:
How are the port and sequence numbers different than before?
Type your answers here.
The source and destination ports are reversed, and the acknowledgement number is 1. The flags
have changed to SYN+ACK.
i. Click the HTTP PDU which HTTP Client has prepared to send to MultiServer. This is the beginning of
the HTTP communication. Click this second PDU envelope and select Outbound PDU Details.
Question:
What information is now listed in the TCP section? How are the port and sequence numbers different
from the previous two PDUs?
Type your answers here.
The source and destination ports are reversed, both sequence number is 1, the acknowledgement
number is 103 (value my vary), and the flags are PSH and ACK.
j. Reset the simulation.
2013 - 2020 Cisco and/or its affiliates. All rights reserved. Cisco Public Page 3 of 6 www.netacad.com
Packet Tracer - TCP and UDP Communications
Step 2: Examine FTP traffic as the clients communicate with the server.
a. Open the command prompt on the FTP Client desktop. Initiate an FTP connection by entering ftp
192.168.1.254.
b. In the Simulation Panel, change Edit Filters to display only FTP and TCP.
c. Click Capture/Forward. Click the second PDU envelope to open it.
Click the Outbound PDU Details tab and scroll down to the TCP section.
Question:
How are the port and sequence numbers different than before?
Type your answers here.
21, 1025, 0, 1. SYN+ACK. The source and destination ports are reversed, and the
acknowledgement number is 1.
g. Click the Outbound PDU Details tab.
Question:
How are the port and sequence numbers different from the previous results?
Type your answers here.
1025, 21, 1, 1. The source and destination ports are reversed, and both sequence and
acknowledgement numbers are 1.
h. Close the PDU and click Capture/Forward until a second PDU returns to the FTP Client. The PDU is a
different color.
i. Open the PDU and select Inbound PDU Details. Scroll down past the TCP section.
Question:
Step 3: Examine DNS traffic as the clients communicate with the server.
a. Repeat the steps in Part 1 to create DNS traffic.
b. In the Simulation Panel, change Edit Filters to display only DNS and UDP.
c. Click the PDU envelope to open it.
d. Look at the OSI Model details for the outbound PDU.
Question:
2013 - 2020 Cisco and/or its affiliates. All rights reserved. Cisco Public Page 4 of 6 www.netacad.com
Packet Tracer - TCP and UDP Communications
How are the port and sequence numbers different than before?
Type your answers here.
53, 1025. The source and destination ports are reversed.
What is the last section of the PDU called? What is the IP address for the name multiserver.pt.ptu?
Type your answers here.
DNS ANSWER, 192.1681.254.
h. Click Reset Simulation.
Step 4: Examine email traffic as the clients communicate with the server.
a. Repeat the steps in Part 1 to send an email to user@multiserver.pt.ptu.
b. In the Simulation Panel, change Edit Filters to display only POP3, SMTP and TCP.
c. Click the first PDU envelope to open it.
d. Click the Outbound PDU Details tab and scroll down to the last section.
Questions:
How are the port and sequence numbers different than before?
Type your answers here.
2013 - 2020 Cisco and/or its affiliates. All rights reserved. Cisco Public Page 5 of 6 www.netacad.com
Packet Tracer - TCP and UDP Communications
25, 1025, 0, 1. SYN+ACK. The source and destination ports are reversed, and the
acknowledgement number is 1.
h. Click the Outbound PDU Details tab.
Question:
How are the port and sequence numbers different from the previous two results?
Type your answers here.
1025, 25, 1, 1. ACK. The source and destination ports are reversed, and both sequence and
acknowledgement numbers are 1. ACK
i. There is a second PDU of a different color that E-Mail Client has prepared to send to MultiServer. This
is the beginning of the email communication. Click this second PDU envelope and select Outbound PDU
Details.
Questions:
How are the port and sequence numbers different from the previous two PDUs?
Type your answers here.
1025, 25, 1, 1. PSH+ACK. The source and destination ports are reversed, and both sequence and
acknowledgement numbers are 1.
What email protocol is associated with TCP port 25? What protocol is associated with TCP port 110?
Type your answers here.
SMTP. POP3.
End of document
2013 - 2020 Cisco and/or its affiliates. All rights reserved. Cisco Public Page 6 of 6 www.netacad.com