5.4.6 Packet Tracer – Use Diagnostic Commands (Answers)
Objectives
Part 1: Gather End User Device Settings
Part 2: Gather Information about Network Devices
Part 3: Diagnose Connectivity Issues
Background / Scenario
In this Packet Tracer (PT) activity, you will use various commands to gather device information and troubleshoot device configuration and connectivity issues. Device information includes IP address, default gateway, and DNS server settings. These settings are critical to enable a device to communicate on networks and connect to the internet.
Instructions
Part 1: Gather End User Device Settings
In this part, you will document the IP address settings for end devices.
Step 1: Document the IP address settings for HQ-Laptop-1.
a. The activity opens in the HQ cluster. The Wiring Closet is the tall, black chassis in the bottom left corner of the first floor. Locate all the devices on the first floor: PCs 1-1, 1-2, 1-3, and 1-4; printer FL-1P; and HQ-Laptop-1.
b. Click HQ-Laptop-1 > Desktop tab > Command Prompt.
c. Enter the ipconfig command.
Questions:
Which IPv4 address is displayed for the Wireless0 Connection?
It may show as 169.254.0.0/16 address because the wireless connection may not be established yet. The address will be within the 192.168.50.0/24 network.
If the IPv4 address is in the 169.254.0.0/16 range, what method is being used to assign IPv4 addresses?
Why is the laptop assigned an IPv4 address in the 169.254.0.0/16 range?
It indicates that the device was unable to obtain addressing from a DHCP server. Therefore, the device assigned itself an address 169.254.0.0/16 pool used for automatic private IP addressing (APIPA).
If the IPv4 address is in the 169.254.0.0/16, wait a few seconds and repeat the ipconfig command.
Questions:
When the IPv4 address is no longer from 169.254.0.0/16 range, what is the IP addressing information displayed? Record your answers in the table below.
| Wireless0 | IP Addressing Information |
|---|---|
| Link-local IPv6 Address | FE80::20A:F3FF:FEE4:EEAA |
| IPv6 Address | :: |
| IPv4 Address | 192.168.50.4 (it may vary, but will be within the 192.168.50.0/24 range) |
| Subnet Mask | 255.255.255.0 |
| Default Gateway | 192168.50.1 |
| DNS Servers | N/A |
Do you see a DNS server address? Explain.
The ipconfig command does not report the DNS server address.
d. Enter the ipconfig /all command.
Question:
Do you see the DNS server address? What is it?
10.2.0.125
Step 2: Document the IP address settings for Net-Admin.
a. Click Wiring Closet > Net-Admin > Desktop tab > Command Prompt.
b. Enter the ipconfig /all command.
Question:
What is the IP addressing information displayed under the FastEthernet0 interface? Record your answers in the table below.
| FastEthernet0 | IP Addressing Information |
|---|---|
| Physical Address | 0001.C910.22D6 (it may vary) |
| Link-local IPv6 Address | FE80::201:C9FF:FE10:22D6 |
| IPv6 Address | :: |
| IPv4 Address | 192.168.99.9 |
| Subnet Mask | 255.255.255.0 |
| Default Gateway | 192168.99.1 |
| DNS Servers | 0.0.0.0 |
Part 2: Gather Information about Network Devices
In this part, you will document information about the link to ISP. You will then document the IP addressing information for all the end devices in HQ and discover that devices belong to different virtual local area networks (VLANs).
Step 1: Gather network connection information about the link between HQ and ISP.
The HQ-Edge router is the router between the HQ network and the ISP. We need to identify the upstream device information located in the ISP.
a. In the Wiring Closet left rack, click HQ-Edge > CLI tab.
b. Press Enter to get the HQ-Edge> prompt, and then enter the enable command.
c. Enter the show ip route | begin Gateway command.
Questions:
What is the address for the gateway of last resort (or default gateway)?
0.0.0.0
Why is the next hop address not displayed?
It is not explicitly configured.
d. Enter the show running-config | begin ip route command.
Question:
How is the default route configured? Does it use the next hop address?
It is configured with the exit interface instead of next hop address.
e. Enter the show cdp neighbors detail command.
Questions:
What is the IPv4 address of the next hop (ISP) address?
10.0.0.49
Which port on the ISP router is connected to HQ-Edge?
GigabitEthernet 1/0
What IOS version is used on the ISP router?
IOS ™ PT1000 Software (PT1000-I-M), Version 12.2(28), RELEASE SOFTWARE (fc5)
f. Enter the ping 10.0.0.49 command.
g. Enter the show arp command.
Question:
What is the MAC address of the interface on the ISP router that is connected to HQ-Edge?
0060.2FE1.903B
h. Close HQ-Edge and exit the Wiring Closet.
Step 2: Gather network connection information about the devices in HQ.
a. From 1-1, 1-2, 1-3, 1-4, FL-1P, and HQ-Laptop-1, use the ipconfig command to find their IPv4 addresses and Default Gateways.
| Device | IPv4 Address | Default Gateway |
|---|---|---|
| 1-1 | 192.168.10.2 | 192.168.10.1 |
| 1-2 | 192.168.10.3 | 192.168.10.1 |
| 1-3 | 192.168.20.2 | 192.168.20.1 |
| 1-4 | 192.168.20.3 | 192.168.20.1 |
| FL-1P | 192.168.50.2 | 192.168.50.1 |
| HQ-Laptop-1 | 192.168.50.3 | 192.168.50.1 |
b. From PC 1-1, open Command Prompt, and then enter the arp -a command.
Question:
What information is displayed?
No ARP Entries Found.
c. Use the ping command to ping 1-2, 1-3, 1-4, FL-1P, and HQ-Laptop-1.
d. Enter the arp -a command.
Questions:
What information is displayed?
Internet Address Physical Address Type
192.168.10.1 000a.41ea.6b47 dynamic
192.168.10.3 0002.4a8a.d20e dynamic
ARP provides a table that maps known MAC addresses to their associated IP
addresses.
Why do the entries in the ARP table not contain information about devices in the 192.168.20.0 and 192.168.50.0 networks while the ping is successful?
192.168.10.0/24, 192.168.20.0/24, and 192.168.50.0/24 are on different VLANs. Ping from 192.168.10.0 network to other VLAN networks would need to go through the default gateway first. Therefore, the ARP table only contains the information about devices within the same network or the same VLAN.
e. To find the route a packet takes to reach the DNS server, enter the tracert 10.2.0.125 command.
Question:
What information is displayed?
Tracing route to 10.2.0.125 over a maximum of 30 hops:
1 0 ms 2 ms 0 ms 192.168.10.1
2 12 ms 0 ms 0 ms 10.0.0.49
3 1 ms 0 ms 0 ms 10.2.0.125
How many routers, or hops, are between PC 1-1 and the DNS server?
2
Part 3: Diagnose Connectivity Issues
In this part, you will use a variety of diagnostic commands and techniques. You will use the nslookup command to query a DNS server and troubleshoot a DNS database. You will then diagnose why a ping fails but web access is successful. Finally, you will use the netstat command to discover which ports are listening on the target device.
Step 1: Test a URL to investigate a connectivity issue.
a. On PC 1-1, close the Command Prompt, and then click Web Browser.
b. Enter the URL test.ptsecurity.com.
Question:
Does the web page display? If not, what is the message?
No, it does not. The message is “Host Name Unresolved”.
c. Enter the IP address 192.168.75.2.
Questions:
Does the web page display?
Yes
Why does the web page display by using the IP address but not the domain name?
The PC cannot resolve the domain name to the IP address.
Step 2: Use the nslookup command to verify DNS service.
a. Close Web Browser, and then click Command Prompt.
b. Enter the ping test.ptsecurity.com command.
Questions:
What message is displayed?
Ping request could not find host test.ptsecurity.com. Please check the name and try again.
What does the message indicate?
The DNS entry is not in the database of the DNS server.
c. Enter the nslookup test.ptsecurity.com command.
Question:
What message is displayed?
Server: [10.2.0.125]
Address: 10.2.0.125
*** UnKnown can't find test.ptsecurity.com: Non-existent domain.
Which server is the default DNS server?
10.2.0.125
d. The nslookup command supports the use of alternate DNS server. Enter the nslookup /? command to learn options available for the command.
e. Enter the nslookup test.ptsecurity.com 192.168.99.3 command and press Enter.
Note: Packet Tracer may take several seconds to converge.
Questions:
What message is displayed?
C:\> nslookup test.ptsecurity.com 192.168.99.3
Server: [192.168.99.3]
Address: 192.168.99.3
Non-authoritative answer:
Name: test.ptsecurity.com
Address: 192.168.75.2
In Step 2c, why is the domain name unable to be resolved?
When a domain name is entered in the URL box, the PC is trying to resolve it through the default DNS server. In this case, the default DNS server does not contain the information in its database.
Step 3: Use output from the ping command to diagnose connectivity issues.
a. Enter the ping mail.cybercloud.com command.
Questions:
What message is displayed?
C:\> ping mail.cybercloud.com
Pinging 172.19.0.4 with 32 bytes of data:
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Ping statistics for 172.19.0.4:
Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),
What information is indicated by the message?
The DNS name resolution is successful. However, the ping failed. Possible reasons are that the host is inactive or the ICMP echo/echo-reply is disabled on the host.
b. Enter the ping www.ptsecurity.com command.
Questions:
What message is displayed?
Pinging 10.0.0.3 with 32 bytes of data:
Request timed out.
Request timed out.
Reply from 10.0.0.3: Destination host unreachable.
Reply from 10.0.0.3: Destination host unreachable.
Ping statistics for 10.0.0.3:
Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),
What information is indicated by the message?
There is a firewall in the path that blocks the ping to the destination.
c. Close the Command Prompt, open Web Browser, and then navigate to www.ptsecurity.com.
Questions:
Does the web page display?
Yes
What conclusion can be drawn?
The web host is running; however, the ping to the web server is blocked.
Step 4: Use the netstat command to find active and listening ports.
a. Close Web Browser, and reopen Command Prompt.
b. In HQ, click the Wiring Closet
c. From the right rack, click the FTP server > Desktop tab > Command Prompt.
d. Arrange the PC 1-1 and FTP server Command Prompt windows side by side.
e. From the PC 1-1 window, enter the netstat command.
Questions:
What message is displayed? Does it show any data?
C:\>netstat
Active Connections
Proto Local Address Foreign Address State
C:\>
No data is shown.
f. From the FTP server, enter the netstat command.
Question:
What message is displayed? Does it show any data?
C:\>netstat
Active Connections
Proto Local Address Foreign Address State
TCP 0.0.0.0:25 0.0.0.0:0 CLOSED
TCP 0.0.0.0:110 0.0.0.0:0 CLOSED
TCP 0.0.0.0:8443 0.0.0.0:0 CLOSED
C:\>
It shows no active connection to other devices and no listening ports.
g. On FTP server, enter the ipconfig command to determine its IP address.
h. From PC 1-1, start an FTP session with the FTP server.
i. On the FTP server, enter the netstat command.
Questions:
What message is displayed? Is there any new information?
Yes, a new entry shows TCP 192.168.75.2:21 192.168.10.3:1025 ESTABLISHED.
Which port is the listening port and what is the status of the connection?
The listening port is TCP 21 and the TCP connection is established.
j. From PC 1-1, enter bob as the username.
k. From the FTP server, enter the netstat command.
Question:
Does the displayed information change?
No.
l. From PC 1-1, enter cisco123 as the password.
m. From PC 1-1, enter the dir command.
n. From the FTP server, enter the netstat command.
Questions:
Does the displayed information change?
Yes. A new entry shows TCP 192.168.75.2:1028 192.168.10.3:1028 CLOSED.
What is indicated by this new entry?
A new TCP connection is opened to transfer the file names in the FTP directory and the connection is closed after the operation completes.
o. From PC 1-1, enter the put Sample2.txt command and press Enter. This will upload the Sample2.txt file to the FTP server.
p. From the FTP server, enter the netstat command.
Questions:
Does the displayed information change?
Yes. A new entry shows:
TCP 192.168.75.2:1030 192.168.10.3:1029 CLOSING.
q. Wait for a few seconds and then enter the netstat command again.
Question:
Does the displayed information change?
Yes. The “CLOSING” line is gone.
r. From PC 1-1, enter the quit command.
s. From the FTP server, enter the netstat command.
Question:
Does the displayed information change?
Yes. Now the TCP connection between 192.168.75.2:21 and 192.168.10.2:1027 is CLOSED.
t. From PC 1-1, close Command Prompt, and then open Web Browser.
u. Navigate to 192.168.75.2.
v. From the FTP server, enter the netstat command.
Questions:
Does the displayed information change?
Yes. A new entry shows TCP 192.168.75.2:80 192.168.10.2:1030 CLOSED.
What does this new entry indicate?
A web page request is made by the host 192.168.10.2. The web page is transmitted (displayed on the web browser of PC 1-1) and the TCP connection is closed.