100-150 Diagnosing Problems Practice Test 2 — 15 Questions

Question 1

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?

Accepted Answer

Run ipconfig on the workstation.. Verifying the IP configuration is essential when network access fails. Using 'ipconfig' allows the technician to see if the PC has a valid address, subnet mask, and gateway. Checking the DHCP server configuration ensures that the scope is not exhausted and that the client is actually communicating with the server. These two steps confirm if the layer 3 addressing is correct before moving on to more complex layer 2 or routing issues.

Answer

Check the switch interface status.

Answer

Perform a traceroute to the local gateway.

Answer

Reset the switch configuration.

Question 2

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

Accepted Answer

The default route is missing.. The routing table shows only local subnets and lacks a gateway of last resort, which is required for routing traffic to external networks like the internet. Without a default route (0.0.0.0/0), the router does not know where to send packets destined for non-local addresses. Configuring a static default route pointing to the ISP is the standard fix to enable internet access on this device.

Answer

The interface is shut down.

Answer

The subnet mask is incorrect.

Answer

The router has no IP address assigned.

Question 3

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

Accepted Answer

To provide a stable interface for management and testing.. A loopback interface is a logical, virtual interface that is always 'up' as long as the router is running. It is primarily used for management, testing, and as a stable source IP for routing protocols like OSPF and BGP. Because it is never dependent on physical cable status, it provides a reliable point for testing connectivity and management access regardless of physical link failures.

Answer

To act as a physical bridge between two VLANs.

Answer

To increase the total bandwidth of the router.

Answer

To provide power over Ethernet to connected devices.

Question 4

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

Accepted Answer

test cable-diagnostics tdr interface <int>. The TDR (Time Domain Reflectometer) feature available on many modern Cisco switches allows the administrator to perform a diagnostic test on the physical copper cable. By sending a pulse of energy and measuring the reflection, the switch can accurately identify if there is an open or short circuit, or if the cable length is within operational limits, providing clear physical layer diagnostic data without additional hardware.

Answer

show cable status

Answer

ping -t <ip>

Answer

show interfaces summary

Question 5

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?

Accepted Answer

DNS. DNS resolution translates human-readable hostnames into IP addresses required for routing across the network. When a user can reach internal services via IP but fails via hostname, the underlying network transport is functional, but the application-layer mapping service is failing. Diagnosing this involves checking the configured DNS server address on the client and verifying connectivity.

Answer

Default Gateway

Answer

DHCP

Answer

ARP

Question 6

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?

Accepted Answer

The DHCP server is unreachable or the scope is full.. The 169.254.0.0/16 range is reserved for Automatic Private IP Addressing (APIPA), which is used when a device is configured for DHCP but cannot reach a server. This diagnostic indicator points directly to a failure in the DORA process. Identifying APIPA addresses helps technicians quickly narrow down connectivity issues to the DHCP server or local cabling.

Answer

The laptop has a duplicate IP address on the network.

Answer

The DNS server is currently offline.

Answer

The subnet mask is incorrectly configured manually.

Question 7

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?

Accepted Answer

Issue the 'shutdown' followed by 'no shutdown' commands.. The 'err-disabled' state is a feature that automatically shuts down a port when certain error conditions are detected, such as port security violations or duplex mismatches. To recover the port manually, the interface must be reset. This process ensures that the administrator acknowledges the error and confirms that the underlying issue has been resolved.

Answer

Reload the entire switch to clear the buffer.

Answer

Change the VLAN assignment of the port.

Answer

Clear the MAC address table for that interface.

Question 8

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.)

Accepted Answer

The approximate round-trip time between source and destination.. The ping utility is a fundamental tool for verifying Layer 3 reachability. It provides critical diagnostic data such as round-trip time and packet loss statistics. Understanding how to interpret ping results allows technicians to distinguish between complete outages, intermittent physical issues, and potential congestion or routing delays within the network path.

Answer

The specific MAC address of the destination device.

Answer

The list of every router hop along the path.

Answer

The TCP port numbers that are currently open on the host.

Question 9

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

Accepted Answer

Duplex mismatch between the switch and the connected host.. Input errors on an interface indicate that the switch received frames it could not process correctly. This is often a sign of physical layer degradation or configuration mismatches. Monitoring these counters is a vital part of proactive network maintenance, as they often precede a total link failure or significantly impact application performance due to retransmissions.

Answer

Excessive broadcast traffic originating from a loop.

Answer

The interface being administratively shut down.

Question 10

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?

Accepted Answer

There is a Layer 2 framing or protocol mismatch.. The 'up/down' status on a Cisco interface specifically points to a Layer 2 problem. This means the physical layer (Layer 1) is sensing a signal, but the data link layer (Layer 2) cannot establish a connection. Common causes include encapsulation mismatches, lack of keepalives, or specific protocol failures like spanning-tree blocking the port.

Answer

The cable is disconnected or the remote device is powered off.

Answer

The interface has been manually disabled by an administrator.

Answer

The IP address has not been assigned to the interface.

Question 11

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?

Accepted Answer

Radio Frequency Interference (RFI) is degrading the signal.. Wireless networks using the 2.4GHz band are highly susceptible to electromagnetic interference from non-802.11 devices. Microwaves and cordless phones operate on similar frequencies, creating noise that disrupts Wi-Fi signals. This results in high packet loss and retransmissions, which the users perceive as slow speeds or intermittent connectivity during peak usage times.

Answer

The Access Point is experiencing a DHCP exhaustion attack.

Answer

The Access Point is configured with the wrong SSID.

Answer

The switch port connecting the Access Point is in half-duplex mode.

Question 12

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?

Accepted Answer

The default gateway address is incorrect.. The default gateway is the local router interface that allows a host to send traffic to remote networks. If a host can communicate locally, its IP and subnet mask are likely correct for the segment, but without a functional gateway, it has no path to send packets destined for any address outside its own subnet.

Answer

The DNS server address is missing.

Answer

The subnet mask is too restrictive.

Answer

The NIC is configured for the wrong duplex mode.

Question 13

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.)

Accepted Answer

IP address for the client.. The DHCP ACK is the final step in the DORA process where the server confirms the lease of an IP address. Understanding the specific parameters delivered in this message is crucial for diagnosing configuration errors that affect host connectivity, name resolution, and the ability of devices to reach resources outside their local network segment.

Answer

The MAC address of the DHCP server.

Answer

The SSH private key for the management console.

Question 14

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?

Accepted Answer

The host on Fa0/2 has not sent any traffic to the switch.. The MAC address table shows which devices are currently communicating through the switch. If a host is connected but its MAC address does not appear in the table, the switch has not received any valid frames from that device. This points to a failure in the initial communication process, likely at the physical or data link layer.

Answer

The switch has learned the MAC address but the port is blocked.

Answer

Port Fa0/2 is configured as a trunk port and is filtering traffic.

Answer

The host on Fa0/2 is using a static IP address.

Question 15

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?

Accepted Answer

The IP addresses are in different subnets.. When two routers are directly connected, they must share the same logical subnet to communicate. If the IP addresses are on different subnets or the subnet masks are mismatched, they will not be able to exchange packets. This is a common configuration error that occurs during initial setup or after a network change.

Answer

The routers are using different routing protocols.

Answer

The DNS server is not configured on the routers.

Answer

The 'no shutdown' command was not issued.