100-150 Diagnosing Problems — All Questions With Answers

Review the full OSPF breakdown →

Refer to the exhibit. A technician sees this status for a switch port. Which action should be taken first?

Exhibit

Interface FastEthernet0/1 is up, line protocol is down.

Question 2mediummulti select

A branch office router reports OSPF neighbor adjacency failures. Which THREE items should be verified to troubleshoot this issue?

Question 3mediummultiple choice

Open the full STP breakdown →

Which symptom is most indicative of a mismatched native VLAN on a trunk link between two Cisco switches?

Question 4hardmultiple choice

During a network audit, a technician finds that an interface is frequently transitioning between up and down states. Which feature should be configured to prevent unnecessary STP topology changes?

Question 5hardmulti select

A technician is diagnosing an intermittent connectivity issue between two switches. Which TWO commands would be most useful for identifying physical layer errors on a specific interface? (Choose two.)

Question 6mediummultiple choice

Read the full DHCP explanation →

A network administrator notices that a host connected to a Cisco Catalyst switch is experiencing extremely slow performance and high collision rates. The switch port is manually configured for 100 Mbps and Full Duplex, while the host is set to Auto-negotiation. Which condition is most likely causing this performance degradation?

Question 7hardmultiple choice

A network technician is troubleshooting why a workstation cannot connect to any network resources. The workstation's NIC shows a link light, and the switch port is not err-disabled. The technician runs ipconfig and sees an IP address of 169.254.10.20 with a subnet mask of 255.255.0.0. The technician then checks the DHCP server and confirms it is operational and has available addresses. Which is the most likely cause of the problem?

Question 8mediummultiple choice

A network administrator notices that a switch interface is showing a high number of CRC errors and late collisions. The interface is connected to a server with a 1000BASE-T connection. Which is the most likely cause of these errors?

Question 9mediummultiple choice

A network administrator observes that a workstation cannot ping its default gateway. The physical link light is active, and the local IP configuration appears correct. Which diagnostic step should be performed first to isolate the layer 2 connectivity issue?

Question 10hardmulti select

Review the full routing breakdown →

A user reports intermittent connectivity to the internal server. Which TWO commands are most useful to identify if the issue is caused by physical layer flapping or interface errors?

Question 11easymultiple choice

A user cannot reach a web server. You perform a ping and it fails, but a traceroute shows the packets reaching the last hop before the server. What does this indicate?

Question 12mediummultiple choice

Which tool is best suited for identifying a slow network segment caused by excessive broadcast traffic?

Question 13mediummultiple choice

Refer to the exhibit. What is the most likely cause of poor performance on this link?

Exhibit

Interface: FastEthernet0/0, Status: Up, Protocol: Up, Errors: 0, Input Rate: 1000 Mbps, Bandwidth: 100 Mbps.

Question 14easymultiple choice

When a network administrator uses the 'ping' command to test connectivity, what is the primary purpose of the ICMP 'Echo Request' and 'Echo Reply' process?

Question 15hardmultiple choice

A network is experiencing high latency. The administrator finds that the switch has high CPU utilization. Which diagnostic step is most appropriate to identify the cause?

Question 16hardmulti select

Review the full routing breakdown →

A network technician is troubleshooting a PC that cannot access internal network resources. Which TWO steps are recommended to verify if the PC is receiving a valid IP address?

Question 17mediummultiple choice

Refer to the exhibit. Why is the router unable to reach the internet?

Exhibit

show ip route
Gateway of last resort is not set
192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.168.1.0/24 is directly connected, GigabitEthernet0/0
L 192.168.1.1/32 is directly connected, GigabitEthernet0/0

Question 18easymultiple choice

Study the full ACL explanation →

What is the primary function of a loopback interface in troubleshooting network devices?

Question 19mediummultiple choice

A technician suspects a cable issue on a copper link. Which command should they use to check for electrical issues like shorts or opens?

Question 20mediummultiple choice

A help desk technician is troubleshooting a user who can access internal network shares using an IP address but cannot reach the same shares using the server's hostname. Which network service should the technician investigate first?

Question 21easymultiple choice

A technician notices a laptop has an IP address of 169.254.11.45. The laptop cannot access the internet or local servers. What is the most likely cause of this issue?

Question 22mediummultiple choice

While troubleshooting a connectivity issue, a technician discovers a switch port is in the 'err-disabled' state. What is the standard first step to attempt to bring the port back online after identifying and fixing the root cause?

Question 23mediummulti select

A network administrator is using the 'ping' command to troubleshoot connectivity. Which TWO pieces of information can be determined specifically from the ICMP Echo Reply messages? (Choose two.)

Question 24hardmulti select

Which THREE conditions are common causes of 'Input Errors' appearing on a Cisco switch interface? (Choose three.)

Question 25mediummultiple choice

Read the full wireless explanation →

Refer to the exhibit. A technician is investigating why a device connected to FastEthernet0/1 cannot communicate. Based on the output, what is the most likely issue?

Exhibit

Switch# show ip interface brief
Interface              IP-Address      OK? Method Status                Protocol
FastEthernet0/1        unassigned      YES unset  up                    down
FastEthernet0/2        192.168.1.1     YES manual up                    up

Question 26mediummultiple choice

Users in an office report that the wireless network is extremely slow during the middle of the day. A technician discovers a microwave oven and several 2.4GHz cordless phones in the breakroom near the Access Point. What is the cause of this performance issue?

Question 27hardmultiple choice

Read the full DHCP explanation →

A technician is troubleshooting a PC that can communicate with other hosts on the same subnet but cannot reach any hosts on different subnets. Which configuration on the PC is most likely incorrect?

Question 28mediummulti select

A network engineer is troubleshooting a potential DHCP issue. Which THREE components are provided to a client during a successful DHCP 'Acknowledgment' (ACK) message? (Choose three.)

Question 29mediummultiple choice

Review the full routing breakdown →

Refer to the exhibit. A host connected to port FastEthernet0/2 is unable to communicate with other devices in VLAN 10. Based on the output, what can be concluded about port Fa0/2?

Exhibit

Switch# show mac address-table
          Mac Address Table
-------------------------------------------
Vlan    Mac Address       Type        Ports
----    -----------       ----        -----
  10    0050.56be.d57b    DYNAMIC     Fa0/5
  10    000c.29fb.3842    DYNAMIC     Fa0/1
Total Mac Addresses for this criterion: 2

Question 30mediummultiple choice

A technician is troubleshooting a router that can ping its own interface but cannot ping a directly connected router's interface. The technician verifies that both interfaces are 'up/up'. What is the most likely cause?

Question 31hardmultiple choice

A user reports they can access the Internet but cannot connect to a specific internal accounting server. Other users in the same department can access the server without issue. What should the technician check first?

Question 32mediummultiple choice

While monitoring a network, an administrator sees a sudden spike in CPU usage on all switches and very high levels of broadcast traffic. What is the most likely cause of this behavior?

Question 33hardmultiple choice

A technician can successfully ping local servers on the same 192.168.10.0/24 subnet but cannot reach any resources on a different VLAN or the Internet. The technician verifies the local IP address and subnet mask are correct. Which component is the most likely source of the connectivity failure?

Question 34mediummulti select

A user reports they cannot access a web server at 192.168.50.10. Which TWO commands would provide the most useful initial diagnostic information regarding the path and reachability to this destination from a Windows workstation? (Choose two).

Question 35mediummultiple choice

A user on VLAN 20 reports that they cannot reach a server on VLAN 30, but they can reach other devices on VLAN 20 and the Internet. The network uses a Layer 3 switch for inter-VLAN routing. The technician verifies that the user's PC has the correct IP address, subnet mask, and default gateway. Which command should the technician run on the Layer 3 switch to verify that inter-VLAN routing is enabled and functioning?

Question 36easymultiple choice

A help desk technician is troubleshooting a Windows workstation that cannot reach any resources on the local subnet. The technician runs ipconfig /all and notices the workstation has an IP address of 192.168.1.50 with a subnet mask of 255.255.255.0, but the default gateway field is blank. The workstation can ping other hosts on the same subnet. What is the most likely cause of the inability to reach remote networks?

Question 37mediummultiple choice

A technician is troubleshooting a user's workstation that cannot reach any resources on a remote subnet, though local subnet communication works fine. The technician suspects a routing or default gateway issue. Which command should be used on the workstation to verify the configured default gateway address?

Question 38easymultiple choice

A technician is troubleshooting a workstation that cannot reach any network resources. The workstation's IP configuration shows an address of 169.254.10.22 and a subnet mask of 255.255.0.0. Which condition does this indicate?

Question 39easymultiple choice

A user calls the help desk and reports that a laptop cannot reach any websites or internal servers. The technician runs ipconfig and sees that the laptop has an IPv4 address of 169.254.88.12 with a subnet mask of 255.255.0.0 and no default gateway. Which action should the technician take FIRST to resolve the problem?

Question 40mediummultiple choice

A network technician is investigating why a user cannot access a file server at 10.1.1.100. The user's workstation can ping the server successfully, but when the user tries to open a shared folder, the connection times out. The technician verifies that other users can access the same share. Which tool should the technician use to determine if a firewall is blocking the specific file-sharing protocol?

Question 41easymultiple choice

A user reports that they cannot access any websites by name, but they can reach them by typing the IP address directly into the browser. The technician confirms that the workstation has a valid IP address, subnet mask, and default gateway. Which command should the technician use to test whether the DNS server is responding to queries?

Question 42mediummultiple choice

Open the full STP breakdown →

A network administrator is troubleshooting a switch port that connects to a user's PC. The port shows a status of 'err-disabled' and the reason is 'psecure-violation.' Which action should the administrator take first to resolve this?

Question 43mediummultiple choice

A network administrator is troubleshooting a switch that is experiencing high CPU utilization. The administrator suspects a switching loop. Which command should be used to verify whether Spanning Tree Protocol has blocked any ports to prevent a loop?

Question 44hardmultiple choice

A technician is investigating why a user cannot access a web server at 10.1.1.50. The technician runs 'ping 10.1.1.50' and receives a reply, but when the user tries to access the web server via its hostname 'intranet.corp.local', it fails. The user's workstation has a DNS server configured as 10.1.1.10. Which command should the technician use to verify DNS resolution?

Question 45mediummultiple choice

A network technician is troubleshooting a workstation that cannot reach any resources on a remote subnet. The workstation can ping its default gateway and other hosts on the local subnet. The technician runs 'tracert' from the workstation to a remote server and sees the first hop (the default gateway) respond, but all subsequent hops time out. Which is the most likely cause?

Question 46hardmultiple choice

A network technician is troubleshooting a connectivity issue between two switches. The link between them is up, but users on one switch cannot reach devices on the other. The technician suspects a VLAN mismatch. Which command should be used on a Cisco switch to verify the VLAN assignments on a specific interface?

Question 47mediummultiple choice

A technician is troubleshooting a workstation that can reach servers on the local subnet but cannot reach any host on a remote subnet. The workstation's IP address, subnet mask, and DNS server are correct, and pinging the default gateway succeeds. Which command should the technician use to verify the workstation's default gateway and interface configuration?

Question 48hardmultiple choice

A network technician is troubleshooting intermittent connectivity to a server. The technician suspects a duplex mismatch on a switch port connected to the server. Which command should be used to check the duplex setting and error statistics on the switch port?

Question 49hardmulti select

Read the full DHCP explanation →

A network administrator is troubleshooting a Cisco Catalyst switch where a host connected to port Gi1/0/10 is experiencing intermittent connectivity. The administrator suspects a physical layer issue. Which TWO commands would provide the most direct evidence of physical layer problems on that interface? (Choose two.)

Question 50mediummulti select

A technician is troubleshooting a workstation that cannot connect to the network. The workstation has a link light, but ipconfig shows an IP address of 169.254.10.20. The technician suspects a DHCP-related issue. Which two commands should the technician use to attempt to obtain a new IP address from the DHCP server? (Choose two.)

Question 51mediummulti select

Users on a floor of an office building report that file transfers to a server are slow and sometimes stall. The technician suspects a duplex mismatch on the switch port connecting the server. Which TWO symptoms or outputs would confirm a duplex mismatch on that link? (Choose two.)

Question 52hardmulti select

A network administrator is troubleshooting a workstation that cannot access network resources. The administrator runs the command arp -a and sees an incomplete entry for the default gateway. Which two actions should the administrator take to resolve the issue? (Choose two.)

Question 53mediummultiple choice

A network administrator is troubleshooting a connectivity issue between two devices on the same VLAN. The administrator suspects a duplex mismatch on a switch port. Which command should be used on the Cisco switch to verify the duplex settings and error statistics on the interface?

Question 54easymultiple choice

A user reports that they cannot access any websites by name, but they can access websites by typing their IP addresses directly into the browser. The user's computer has a valid IP address, subnet mask, and default gateway, and can ping the default gateway successfully. Which is the most likely cause of the problem?

Question 55hardmultiple choice

A technician is troubleshooting a wireless client that associates successfully with an access point but cannot obtain an IP address from the DHCP server on the wired network. The access point is configured with a management IP on the correct VLAN, and other wired clients on that VLAN obtain leases normally. Which is the MOST likely cause?

Question 56hardmulti select

A technician is troubleshooting a workstation that cannot connect to the network. The workstation has a valid IP address, subnet mask, and default gateway. The technician can ping the default gateway but cannot ping a server on a remote subnet. Which two commands should the technician use to further isolate the problem? (Choose two.)

Question 57hardmultiple choice

A network engineer is investigating why a switch port Gi1/0/5 is not forwarding traffic, even though the connected device is powered on and the cable is known to be good. The engineer runs 'show interfaces Gi1/0/5 switchport' and sees that the administrative mode is dynamic auto, and the operational mode is access. The port status is 'notconnect'. Which is the most likely reason the port is not forwarding?

Question 58mediummultiple choice

A network technician is investigating why a user cannot reach a public website by its hostname, even though the user can ping the website's IP address successfully. The workstation's default gateway and IP configuration are correct. Which command should the technician run to verify whether the workstation's configured DNS servers are responding?

Question 59mediummultiple choice