Network Troubleshooting

A network technician is performing RF site troubleshooting in a manufacturing facility to resolve persistent wireless connectivity issues. Match each observed wireless symptom or environmental phenomenon on the left with its correct physical root cause or signal behavior on the right.

A network technician is addressing severe voice quality degradation on an enterprise VoIP network following a core router firmware update. Place the technician's troubleshooting procedures in the correct sequence according to the official CompTIA troubleshooting methodology.

A system administrator notices that a newly provisioned server cannot reach destinations outside its local subnet. Arrange the diagnostic actions in the correct logical sequence following standard CompTIA troubleshooting methodology.

A network technician needs to identify which port on a patch panel inside a wiring closet connects to an unlabelled wall outlet in a conference room. Which of the following tools is best suited to trace and locate this cable run?

A network technician terminates a custom Category 6A unshielded twisted-pair (UTP) cable run between a high-density patch panel and an enterprise core switch. A basic LED wiremapper confirms pin-to-pin continuity on all eight conductors (pins 1 through 8 match identically on both ends). However, when connected to $10\text{ Gbps}$ switch interfaces, the link fails to auto-negotiate above $100\text{ Mbps}$ and generates a rapid accumulation of Cyclic Redundancy Check (CRC) errors and Near-End Crosstalk (NEXT) violations under traffic load. Which of the following physical layer faults is the root cause of this failure, and which instrument must be used to diagnose it accurately?

A network engineer is systematically troubleshooting a client workstation that is experiencing intermittent domain name resolution failures for internal corporate servers. Arrange the troubleshooting steps in the correct, logical order—beginning with local client configuration verification and progressing outward to network transport validation.

A network administrator receives a report that a newly assigned workstation on VLAN 25 ($10.25.0.0/24$) cannot access remote intranet services. Upon inspecting the workstation, the administrator observes an auto-configured IPv4 address of $169.254.42.10$. Place the following diagnostic and remediation steps in the correct logical sequence to systematically troubleshoot and resolve this DHCP relay issue from client verification to final resolution.

An IT technician is troubleshooting severe throughput degradation and excessive frame retransmissions on a newly configured 2.4 GHz wireless network in an office suite. A site survey reveals that three nearby access points serving the area are operating on channels 1, 3, and 5. Which of the following modifications should the technician make to resolve the interference?

During a post-maintenance outage, voice over IP (VoIP) endpoints on a newly provisioned voice VLAN fail to register with the local SIP call manager. A network engineer formulates a hypothesis that a newly applied transport layer security (TLS) certificate authority (CA) bundle is missing on the automated provisioning server payload. To test this theory, the engineer sets up an isolated test bench, captures the boot traffic of a test phone via switch port mirroring, and inspects the packet trace. The trace confirms that the phone aborts the session during the TLS handshake due to an untrusted certificate authority, successfully validating the root cause. Which of the following actions should the engineer perform NEXT according to the CompTIA troubleshooting methodology?

A network technician is testing connectivity on a workstation that fails to load external websites. The technician executes `nslookup portal.vendor.com` in the command prompt and receives the following output:

text
C:\> nslookup portal.vendor.com
DNS request timed out.
timeout was 2 seconds.
Server: UnKnown
Address: 192.168.1.50

*** Request to UnKnown timed out

Which of the following is the most likely reason for this DNS resolution failure?

A network administrator receives a ticket stating that a newly deployed application server at $192.168.20.5/24$ cannot reach a remote database server located on a different subnet at $10.1.50.10/24$. Place the following diagnostic and remediation steps in the correct logical troubleshooting sequence to isolate and resolve the issue.

A network administrator is investigating connectivity issues where branch office users report that cloud-hosted file transfers repeatedly stall and disconnect over an IPsec VPN tunnel. The administrator tests a hypothesis by sending ICMP packets with the Don't Fragment (DF) bit set, confirming that an maximum transmission unit (MTU) mismatch across the WAN interface is causing packet fragmentation drops. According to the CompTIA troubleshooting methodology, which action should the administrator perform NEXT?

A network administrator runs the following command on a host experiencing name resolution failures:

C:\> nslookup app.corp.local 192.168.1.10
Server: dns01.corp.local
Address: 192.168.1.10

*** dns01.corp.local can't find app.corp.local: Non-existent domain

Based on the output, which TWO of the following represent plausible root causes for this error? (Select TWO.)

A user's workstation is assigned a static IPv4 address of $192.168.1.50$ with a subnet mask of $255.255.255.0$. The default gateway is configured as $192.168.2.1$. The user cannot access any external resources or communicate outside the local network segment. Which of the following best explains why the workstation cannot reach the default gateway?

A network technician is troubleshooting DNS resolution issues on a branch office workstation. The workstation is configured to use the local branch gateway router ($192.168.10.1$) as its primary DNS server, which should forward requests for internal corporate resources to the core DNS server ($10.100.1.5$).

When attempting to resolve an internal hostname, the technician runs the following command-line queries from the workstation:

text
$ nslookup intranet.corp.local
Server: 192.168.10.1
Address: 192.168.10.1#53

** server can't find intranet.corp.local: SERVFAIL

$ nslookup intranet.corp.local 10.100.1.5
Server: 10.100.1.5
Address: 10.100.1.5#53

Name: intranet.corp.local
Address: 10.100.20.50

Based on the output, which TWO of the following are the most likely root causes for the initial resolution failure? (Select TWO.)

A network technician is troubleshooting a workstation that can ping other local hosts on the $192.168.10.0/24$ subnet but cannot access any remote servers on external networks. Running an IP configuration utility displays the following settings:

- IP Address: $192.168.10.45$
- Subnet Mask: $255.255.255.0$
- Default Gateway: $192.168.20.1$

Which of the following configuration issues is preventing the workstation from reaching external networks?

A network technician is troubleshooting an issue where a newly deployed application server ($10.40.20.50/24$) in VLAN 20 cannot connect to an off-site database cluster at $172.16.100.25/24$. Hosts in VLAN 20 can reach local resources and the internet, but cannot communicate with the $172.16.100.0/24$ network. Following the standard CompTIA network troubleshooting methodology, place the diagnostic and remediation steps in the correct sequential order from first to last.

A network administrator is analyzing console log messages and packet captures between two Layer 2 switches, Switch-A and Switch-B, connected via an 802.1Q trunk on port GigabitEthernet0/1. Switch-A has GigabitEthernet0/1 configured with 'switchport trunk native vlan 10', whereas Switch-B has GigabitEthernet0/1 configured with 'switchport trunk native vlan 20'. Cisco Discovery Protocol (CDP) alerts report a %CDP-4-NATIVE_VLAN_MISMATCH error. Hosts on Switch-A in VLAN 10 report unexpected cross-talk and data leaks to hosts on Switch-B in VLAN 20, while tagged VLAN 30 traffic functions normally. Which of the following correctly explains the underlying root cause of this behavior and the required resolution?

A network administrator configures a workstation with IP address $172.20.30.45$ and subnet mask $255.255.255.192$. The workstation can successfully ping local hosts, but fails to reach any external subnets. Reviewing `ipconfig /all` reveals the following output:

IPv4 Address. . . . . . . . . . . : 172.20.30.45
Subnet Mask . . . . . . . . . . . : 255.255.255.192
Default Gateway . . . . . . . . . : 172.20.30.65

Which of the following identifies the root cause of the connectivity failure?

A network technician is investigating a connectivity issue where a host with IP address $172.16.5.25/24$ cannot access services on a remote subnet $10.10.1.0/24$. Local ping tests confirm the host can communicate with other devices on $172.16.5.0/24$. Which of the following misconfigurations could cause this issue? (Select TWO.)