Cisco 100-150 Online Practice Questions and Exam Preparation

Cisco 100-150 Online Questions & Answers

• Question 1:

  A user reports that a company website is not available. The help desk technician issues a tracert command to determine if the server hosting the website is reachable over the network. The output of the command is shown as follows: What can you tell from the command output?

  

  A. The router at hop 3 is not forwarding packets to the IP address 192.168.1.10.
  B. The server address 192.168.1.10 is being blocked by a firewall on the router at hop 3.
  C. The server with the address 192.168.1.10 is reachable over the network.
  D. Requests to the web server at 192.168.1.10 are being delayed and time out.
  C. The server with the address 192.168.1.10 is reachable over the network.

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  Explanation

  The tracert command output shows the path taken to reach the destination IP address, 192.168.1.10. The command output indicates:

  Hops 1 and 2 are successfully reached.

  Hop 3 times out, meaning the router at hop 3 did not respond to the tracert request. However, this does not necessarily indicate a problem with forwarding packets, as some routers may be configured to block or not respond to ICMP requests.

  Hops 4 and 5 are successfully reached, with hop 5 being the destination IP 192.168.1.10, indicating that the server is reachable.

• Question 2:

  HOTSPOT

  You want to list the IPv4 addresses associated with the host name www.companypro.net.

  Complete the command by selecting the correct option from each drop-down list.

  

  

  Explanation

  To list the IPv4 addresses associated with the host name www.companypro.net, you should use the following command:

  nslookup www.companypro.net

  This command will query the DNS servers to find the IP address associated with the hostname provided. If you want to ensure that it returns the IPv4 address, you can specify the -type=A option, which stands for Address records that hold IPv4 addresses1. However, the nslookup command by default should return the IPv4 address if available.

  To list the IPv4 addresses associated with the host name www.companypro.net, you should use the nslookup command.

  Command: nslookup

  Target: www.companypro.net

  So, the completed command is:

  nslookup www.companypro.net

  nslookup: This command is used to query the Domain Name System (DNS) to obtain domain name or IP address mapping or for any other specific DNS record.

  www.companypro.net: This is the domain name you want to query to obtain its associated IP addresses.

  References:

  Using nslookup: nslookup Command Guide

• Question 3:

  Examine the following output:

  

  Which two conclusions can you make from the output of the tracert command? (Choose 2.) Note: You will receive partial credit for each correct answer.

  A. The trace successfully reached the www.cisco.com server.
  B. The trace failed after the fourth hop.
  C. The IPv6 address associated with the www.cisco.com server is 2600:1408: c400: 38d: : b33.
  D. The routers at hops 5 and 6 are offline.
  E. The device sending the trace has IPv6 address 2600:1408:c400:38d :: b33.
  A. The trace successfully reached the www.cisco.com server.
  C. The IPv6 address associated with the www.cisco.com server is 2600:1408: c400: 38d: : b33.

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  Explanation

  A: "The trace successfully reached the www.cisco.com server." This is true as indicated by the "Trace complete" message at the end, showing that the trace has reached its destination.

  C: "The IPv6 address associated with the www.cisco.com server is 2600:1408:c400:38d::b33." This is true because the final hop in the trace, which is the destination, has this IPv6 address.

  B: "The trace failed after the fourth hop." This is incorrect as the trace continues beyond the fourth hop, despite some intermediate timeouts.

  D: "The routers at hops 5 and 6 are offline." This is not necessarily true. The routers might be configured to not respond to traceroute requests.

  E: "The device sending the trace has IPv6 address 2600:1408:c400:38d::b33." This is incorrect; this address belongs to the destination server, not the sender.

• Question 4:

  What is the most compressed valid format of the IPv6 address 2001 :0db8:0000:0016:0000:001b: 2000:0056?

  A. 2001:db8: : 16: : 1b:2:56
  B. 2001:db8: : 16: : 1b: 2000: 56
  C. 2001:db8: 16: :1b:2:56
  D. 2001:db8: 0:16: :1b: 2000:56
  D. 2001:db8: 0:16: :1b: 2000:56

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  Explanation

  IPv6 addresses can be compressed by removing leading zeros and replacing consecutive groups of zeros with a double colon (::). Here's how to compress the address 2001:0db8:0000:0016:0000:001b:2000:0056:

  Remove leading zeros from each segment:

  2001:db8:0000:0016:0000:001b:2000:0056 becomes 2001:db8:0:16:0:1b:2000:56

  Replace the longest sequence of consecutive zeros with a double colon (::). In this case, the two consecutive zeros between the 16 and 1b:

  2001:db8:0:16::1b:2000:56

• Question 5:

  In the network shown in the following graphic, Switch1 is a Layer 2 switch.

  

  PC-A sends a frame to PC-C. Switch1 does not have a mapping entry for the MAC address of PC-C. Which action does Switch1 take?

  A. Switch1 queries Switch2 for the MAC address of PC-C.
  B. Switch1 drops the frame and sends an error message back to PC-A.
  C. Switch1 floods the frame out all active ports except port G0/1.
  D. Switch1 sends an ARP request to obtain the MAC address of PC-C.
  C. Switch1 floods the frame out all active ports except port G0/1.

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  Explanation

  Understanding How Layer 2 Switches Handle Unknown MAC Addresses

  Switches operate at Layer 2 (Data Link Layer) of the OSI model and maintain a MAC address table (CAM table) to forward frames efficiently.

  When a switch receives a frame, it checks its MAC address table to see if it knows the destination MAC address.

  If the destination MAC address is not in the table (meaning the switch does not know which port leads to PC-C), the switch follows the flooding behavior .

  What Happens When Switch1 Receives a Frame from PC-A to PC-C?

  Switch1 checks its MAC table:

  The source MAC (PC-A) is recorded in the table on port G0/1 .

  The destination MAC (PC-C) is not in the table .

  Switch1 does not know where PC-C is:

  It floods the frame out of all active ports except the port it was received on (G0/1) .

  This means the frame is sent to:

  Switch2 (via G0/23)

  PC-B (via G0/2)

  Switch2 receives the frame and follows the same process:

  If Switch2 has PC-C's MAC in its table, it forwards the frame appropriately.

  If not, it floods the frame again until PC-C replies.

  Once PC-C responds, Switch1 and Switch2 learn its MAC address and update their tables.

  Why Other Options Are Incorrect:

  # A. Switch1 queries Switch2 for the MAC address of PC-C.

  Incorrect: Switches do not query other switches directly for MAC addresses. Instead, they rely on learning MAC addresses dynamically through frame forwarding.

  #

  B. Switch1 drops the frame and sends an error message back to PC-A.

  Incorrect: Switches do not drop frames for unknown MAC addresses . Instead, they flood the frames out all ports except the incoming port.

  #

  D. Switch1 sends an ARP request to obtain the MAC address of PC-C.

  Incorrect:

  ARP (Address Resolution Protocol) is only used to resolve IP addresses to MAC addresses .

  Since PC-A is sending a frame (Layer 2), not an IP packet (Layer 3) , ARP is not involved here.

  Conclusion

  Since Switch1 does not know the destination MAC address , it floods the frame out all active ports except the port it was received on . This is the default behavior of Layer 2 switches when they encounter an unknown MAC address.

• Question 6:

  During the data encapsulation process, which OSI layer adds a header that contains MAC addressing information and a trailer used for error checking?

  A. Network
  B. Transport
  C. Data Link
  D. Session
  C. Data Link

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  Explanation

  During the data encapsulation process, the Data Link layer of the OSI model is responsible for adding a header that contains MAC addressing information and a trailer used for error checking. The header typically includes the source and destination MAC addresses, while the trailer contains a Frame Check Sequence (FCS) which is used for error detection.

  The Data Link layer ensures that messages are delivered to the proper device on a LAN using hardware addresses and translates messages from the Network layer into bits for the Physical layer to transmit. It also controls how data is placed onto the medium and is received from the medium through the physical hardware.

• Question 7:

  A host is given the IP address 172.16.100.25 and the subnet mask 255.255.252.0. What is the CIDR notation for this address?

  A. 172.16.100.25 /23
  B. 172.16.100.25 /20
  C. 172.16.100.25 /21
  D. 172.16.100.25 /22
  D. 172.16.100.25 /22

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  Explanation

  The CIDR (Classless Inter-Domain Routing) notation for the subnet mask 255.255.252.0 is /22. This notation indicates that the first 22 bits of the IP address are used for network identification, and the remaining bits are used for host addresses within the network.

• Question 8:

  Which protocol is used to automatically assign IP addresses to devices on a network?

  A. DNS
  B. HTTP
  C. DHCP
  D. SNMP
  C. DHCP

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  Explanation

  Dynamic Host Configuration Protocol (DHCP) is used to automatically assign IP addresses and other network configuration parameters to devices in a network.

• Question 9:

  Which standard contains the specifications for Wi-Fi networks?

  A. GSM
  B. LTE
  C. IEEE 802.11
  D. IEEE 802.3
  E. EIA/TIA 568A
  C. IEEE 802.11

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  Explanation

  The IEEE 802.11 standard contains the specifications for Wi-Fi networks. It is a set of media access control (MAC) and physical layer (PHY) specifications for implementing wireless local area network (WLAN) computer communication in various frequencies, including but not limited to 2.4 GHz, 5 GHz, and 6 GHz1. This standard is maintained by the Institute of Electrical and Electronics Engineers (IEEE) and is commonly referred to as Wi-Fi. The standard has evolved over time to include several amendments that improve speed, range, and reliability of wireless networks.

• Question 10:

  A user initiates a trouble ticket stating that an external web page is not loading. You determine that other resources both internal and external are still reachable. Which command can you use to help locate where the issue is in the network path to the external web page?

  A. ping -t
  B. tracert
  C. ipconfig/all
  D. nslookup
  B. tracert

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  Explanation

  The tracert command is used to determine the route taken by packets across an IP network. When a user reports that an external web page is not loading, while other resources are accessible, it suggests there might be an issue at a certain point in the network path to the specific web page. The tracert command helps to diagnose where the breakdown occurs by displaying a list of routers that the packets pass through on their way to the destination. It can identify the network segment where the packets stop progressing, which is valuable for pinpointing where the connectivity issue lies.

  References: Cisco CCST Networking Certification FAQs ?CISCONET Training Solutions, Command Prompt (CMD): 10 network-related commands you should know, Network Troubleshooting Commands Guide: Windows, Mac and Linux -

  Comparitech, How to Use the Traceroute and Ping Commands to Troubleshoot Network, Network Troubleshooting Techniques: Ping, Traceroute, PathPing.

  Tracert Command: This command is used to determine the path packets take to reach a destination. It lists all the hops (routers) along the way and can help identify where the delay or failure occurs.

  Ping -t: This command sends continuous ping requests and is useful for determining if a host is reachable but does not provide path information.

  Ipconfig /all: This command displays all current TCP/IP network configuration values and can be used to verify network settings but not to trace a network path.

  Nslookup: This command queries the DNS to obtain domain name or IP address mapping, useful for DNS issues but not for tracing network paths.