100-150 Diagnosing Problems Practice Test 3 — 15 Questions

Question 1

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?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

An Access Control List (ACL) blocking the user's IP.. When a single user is restricted from a specific resource that others can reach, the issue is often a specific security policy or local configuration. Access Control Lists (ACLs) can be applied based on source IP addresses, meaning one specific host could be blocked while its neighbors are allowed. This requires investigating the router or firewall policies.

Answer

The status of the default gateway.

Answer

The health of the DNS server.

Answer

A duplex mismatch on the user's switch port.

Question 2

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?

Accepted Answer

A Layer 2 loop in the topology.. A switching loop occurs when there are multiple active paths between switches without Spanning Tree Protocol (STP) preventing a loop. This causes broadcast frames to circulate endlessly, multiplying and consuming all available bandwidth and CPU resources. This 'broadcast storm' is a critical Layer 2 failure that can bring down an entire network.

Answer

A malfunctioning DHCP server.

Answer

An IP address conflict on the gateway.

Answer

The use of the 'traceroute' command by a user.

Question 3

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?

Accepted Answer

Misconfigured default gateway. Successful communication within a local subnet proves that the Network Interface Card and local switching are functional. However, the inability to reach remote networks typically indicates a configuration error regarding the default gateway. Technicians must verify that the gateway address resides on the local subnet and that the router is actively forwarding traffic for that specific VLAN.

Answer

Incorrect DNS server

Answer

Duplicate IP address

Answer

Faulty Cat6 cabling

Question 4

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).

Accepted Answer

ping 192.168.50.10. Ping and Traceroute are the primary tools used to diagnose reachability and path issues across an IP network. Ping tests basic end-to-end connectivity using ICMP Echo Requests, while Traceroute identifies each hop along the path, helping to pinpoint exactly where a packet is being dropped. Mastering these utilities allows technicians to isolate faults between local, ISP, or remote segments.

Answer

ipconfig /renew

Answer

netstat -a

Answer

nslookup 192.168.50.10

Question 5

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?

Accepted Answer

show ip route. The show ip route command reveals the routing table, which on a Layer 3 switch includes directly connected routes for each configured SVI. If inter-VLAN routing is active, the route for the server's VLAN subnet should be present as directly connected. Absence of that route would point to a missing or misconfigured SVI, explaining the connectivity failure.

Answer

show vlan brief

Answer

show interfaces trunk

Answer

show mac address-table

Question 6

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?

Accepted Answer

The default gateway is missing, so the workstation cannot forward traffic to remote networks.. The workstation can ping local hosts, so the local IP and subnet mask are functional. The missing default gateway means the host has no route for destinations outside its own subnet. Without a gateway, packets for remote networks are dropped, which explains why only local communication works. Assigning the correct gateway address restores remote connectivity.

Answer

The DNS server address is not configured, preventing name resolution for remote hosts.

Answer

The workstation is configured with an APIPA address and cannot communicate off-subnet.

Answer

The workstation has an incorrect subnet mask, preventing it from identifying remote networks.

Question 7

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?

Accepted Answer

ipconfig /all. When a workstation can communicate on the local subnet but fails to reach remote networks, the default gateway configuration is a primary suspect. The ipconfig /all command on Windows provides a comprehensive view of the IP configuration, including the default gateway address, allowing the technician to confirm whether it is correctly set or missing.

Answer

ping localhost

Answer

netstat -r

Answer

nslookup

Question 8

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?

Accepted Answer

The workstation is using an APIPA address because it could not contact a DHCP server.. The 169.254.0.0/16 address range is reserved for APIPA, which a host self-assigns when its DHCP discover broadcasts receive no response. This means the workstation has no valid IP, gateway, or DNS information, explaining why all network resources are unreachable. The correct diagnosis is a DHCP communication failure, not a configuration conflict or gateway error.

Answer

The workstation successfully received an IP address from a DHCP server.

Answer

The workstation has a static IP address that conflicts with another device.

Answer

The workstation is configured with an incorrect default gateway.

Question 9

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?

Accepted Answer

Check the physical Ethernet cable and the switch port link status for the laptop.. An address in the 169.254.0.0/16 range is assigned automatically by the operating system when DHCP attempts fail, so the laptop never obtained a valid lease. The most likely causes are a disconnected or faulty cable, a disabled switch port, or a VLAN mismatch. Confirming the physical link and the switch port status is the fastest, least disruptive first step before changing any server or client configuration.

Answer

Restart the DHCP service on the Windows server that serves the user's subnet.

Answer

Configure a static IP address, subnet mask, and default gateway on the laptop.

Answer

Clear the DNS resolver cache on the laptop with ipconfig /flushdns.

Question 10

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?

Accepted Answer

telnet 10.1.1.100 445. Successful ping proves IP reachability, but file sharing uses TCP ports such as 445 or 139. A firewall could block those ports while allowing ICMP. Testing TCP port 445 with telnet determines whether the SMB service is reachable. If telnet fails, a firewall or service problem is indicated; if it succeeds, the issue may be at the application or authentication layer.

Answer

tracert 10.1.1.100

Answer

ping 10.1.1.100 -t

Answer

nslookup 10.1.1.100

Question 11

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?

Accepted Answer

nslookup. The ability to reach websites by IP address but not by name strongly suggests a DNS resolution problem. The nslookup command directly queries the DNS server, allowing the technician to confirm whether the server is reachable and resolving names correctly. If nslookup fails, the technician can then investigate DNS server configuration or network connectivity to the DNS server.

Answer

tracert 8.8.8.8

Answer

ping 8.8.8.8

Answer

ipconfig /release

Question 12

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?

Accepted Answer

Remove the unauthorized device or MAC address causing the port security violation.. The 'psecure-violation' reason indicates that port security has detected an unauthorized MAC address on the interface. The administrator must first identify and remove the device or MAC address causing the violation, or adjust the port security configuration if the device is legitimate. Simply re-enabling the port without resolving the violation will cause it to become err-disabled again.

Answer

Shut down and re-enable the interface with the shutdown and no shutdown commands.

Answer

Configure the port as a trunk to allow multiple MAC addresses.

Answer

Replace the Ethernet cable connecting the PC to the switch port.

Question 13

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?

Accepted Answer

show spanning-tree. Spanning Tree Protocol prevents loops by blocking redundant ports. When a loop is suspected, checking STP status is essential. The show spanning-tree command provides detailed information about port roles and states, including which ports are blocking. If STP is functioning correctly, it will have blocked ports to break the loop, though high CPU may still occur during topology changes.

Answer

show interfaces status

Answer

show running-config

Answer

show mac address-table

Question 14

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?

Accepted Answer

nslookup intranet.corp.local. Since the IP address is reachable but the hostname fails, the problem is name resolution. The nslookup command directly queries the DNS server and shows whether it can resolve intranet.corp.local to the correct IP. This isolates the failure to DNS rather than network connectivity, allowing the technician to further investigate the DNS server or its records.

Answer

ipconfig /all

Answer

arp -a

Answer

tracert 10.1.1.50

Question 15

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?

Accepted Answer

The default gateway is missing a route to the remote subnet.. The workstation can reach its default gateway and local subnet, so local configuration and Layer 1-3 connectivity are fine. The traceroute shows the gateway responding but no further hops, indicating the gateway cannot forward packets to the remote subnet. This is consistent with a missing route on the gateway. An incorrect subnet mask or DNS issue would not produce this exact pattern, and a remote firewall would not stop intermediate hops from responding.

Answer

The workstation's DNS server is unreachable.

Answer

A firewall on the remote server is blocking ICMP echo requests.

Answer

The workstation has an incorrect subnet mask.