Network Troubleshooting

A system administrator suspects a Windows workstation has been compromised and is sending outbound traffic to an unknown command-and-control server. The administrator opens Command Prompt to determine which local Process ID (PID) is responsible for establishing active outbound socket connections. Which command-line utility switch combination should the administrator execute to view numerical IP addresses, active connection states, and their corresponding process IDs?

Users in a regional branch office report that their workstations can successfully communicate with local peers on their LAN segment but are unable to access centralized enterprise resources hosted at $10.50.0.0/24$. A network technician executes `ipconfig /all` on a affected workstation and receives the following output:

text
IPv4 Address. . . . . . . . . . . : 192.168.45.112
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.4.1
DHCP Server . . . . . . . . . . . : 192.168.45.1

Which of the following represents the root cause of the routing failure to external subnets?

During a planned network maintenance window, an administrator installs a new central switch (Switch-Core) to serve as the core switching node. After connecting Switch-Core to the access switches, network traffic follows sub-optimal paths across the campus topology. Troubleshooting reveals that an old edge switch (Switch-Access-3) with a configured Spanning Tree Protocol (STP) bridge priority of 4096 has been elected as the STP root bridge because Switch-Core is using the default STP priority of 32768. Which configuration change on Switch-Core will resolve this issue and establish Switch-Core as the STP root bridge?

A network administrator is troubleshooting an issue where newly deployed host systems on a corporate subnet ($10.100.40.0/24$) can communicate with local peers but fail to reach external subnets or internet services. Executing `ipconfig /all` on one of the affected hosts produces the following output:

text
IPv4 Address. . . . . . . . . . . : 10.100.40.88
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 10.100.4.1
DHCP Server . . . . . . . . . . . : 10.100.1.10

Which of the following options accurately identify the root cause of this connectivity failure and the appropriate corrective action? (Select TWO.)

A network administrator is systematically troubleshooting an end user's workstation that cannot access an internal web application located at `https://app.corp.local`. Place the command-line utility operations in the logical sequential order recommended for isolation, starting from basic local network interface validation up to upper-layer protocol testing.

Match each physical layer cabling symptom or test result on the left with its most likely root cause on the right.

A network technician is troubleshooting an issue on a Linux host that cannot resolve the hostname of an internal server `app.corp.local`. The technician runs `dig app.corp.local` and receives a response indicating `STATUS: SERVFAIL` from the local recursive DNS server at `192.168.1.2`. To determine whether the issue is isolated to the local recursive server or affects the authoritative server directly, the technician wants to query the domain's designated authoritative DNS server at `10.0.5.50`. Which of the following command-line entries should the technician execute?

A network administrator is troubleshooting inter-switch communication between Switch-Alpha and Switch-Beta. Users on VLAN 20 attached to Switch-Alpha report complete loss of connectivity to servers on VLAN 20 attached to Switch-Beta. Additionally, syslog messages indicate that untagged management frames transmitted from Switch-Alpha on VLAN 10 are being received on VLAN 30 on Switch-Beta across trunk interface GigabitEthernet 0/1.

An inspection of the interface configuration reveals:
- Switch-Alpha (GigabitEthernet 0/1): Mode: Trunk, Native VLAN: 10, Allowed VLANs: 10, 20, 30
- Switch-Beta (GigabitEthernet 0/1): Mode: Trunk, Native VLAN: 30, Allowed VLANs: 10, 30

Which TWO configuration adjustments must be implemented on Switch-Beta to resolve both issues? (Select TWO.)

A network technician is troubleshooting an existing Category 6 copper cable run that connects a workstation to a access switch. The link constantly fails to negotiate at Gigabit speed, dropping to 100 Mbps with frequent CRC frame errors under heavy traffic load. A wiremap test confirms that all eight conductors are properly pin-terminated at both ends according to TIA/EIA 568B standards with no open or short circuits. Which diagnostic instrument should the technician use to measure frequency-dependent parameters such as Near-End Crosstalk (NEXT) and return loss to determine if the run meets Category 6 specifications?

A network technician is deploying a new smart HVAC controller on VLAN 55 ($172.16.55.0/24$). The corporate DHCP server is centralized on VLAN 10 ($172.16.10.10/24$). Upon booting up the controller, running a network diagnostics command shows the following output:

IPv4 Address. . . . . . . . . . . : 169.254.108.42
Subnet Mask . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . :
DHCP Enabled. . . . . . . . . . . : Yes

Other existing hosts on VLAN 10 obtain their DHCP leases without issues. Which of the following is the MOST likely cause of the HVAC controller failing to acquire an IP address?

A network administrator is troubleshooting an issue on a Linux server hosting an internal HTTPS application. Users report that they cannot access the website from remote workstations, even though the server is powered on and reachable via `ping`. The administrator executes a command-line utility on the Linux server to inspect active network socket bindings and receives the following output:

State Recv-Q Send-Q Local Address:Port Peer Address:Port Process
LISTEN 0 128 127.0.0.1:443 0.0.0.0:* users:(("httpd",pid=2048,fd=3))

Based on this output snippet, which of the following is the root cause preventing remote clients from accessing the web service?

A network administrator connects a single-mode fiber optic patch cable to a newly installed patch panel module. Although physical link connectivity is established, optical testing shows exceptionally high optical return loss (back reflection), degrading signal quality. Upon visual inspection of the patch panel ports and connectors, the administrator notes that the patch cable has green LC connectors while the patch panel bulkhead coupler accepts blue LC connectors. Which of the following physical layer mismatched connection types is causing this issue?

A network technician is investigating degraded performance and intermittent packet drops on a newly terminated Category 6 UTP cable run. When tested with a basic wiremap continuity tester, all eight pins pass with direct 1-to-1 pin mapping. However, the link experiences severe performance issues under load. Which of the following test results or physical characteristics indicate that a split pair condition is the root cause of this failure? (Select TWO.)

A network administrator is troubleshooting a connectivity failure between two switches connected via an 802.1Q trunk link. Host devices assigned to VLAN 10 on Switch-A are unable to communicate with servers on VLAN 10 connected to Switch-B. Inspection of the switch port configurations indicates that port GigabitEthernet 0/1 on Switch-A is configured with VLAN 10 as its native VLAN, while port GigabitEthernet 0/1 on Switch-B uses default VLAN 1 as its native VLAN. Which of the following best explains why VLAN 10 traffic fails to reach its destination across the trunk?

Match each command-line network troubleshooting command to its primary diagnostic function.

A workstation on VLAN 30 ($192.168.30.0/24$) fails to receive an IP address automatically and shows an APIPA address of $169.254.14.88$. A network administrator must systematically isolate the issue from the local host to the centralized network services. Place the troubleshooting steps in the correct logical sequence.

A network administrator receives reports that mobile devices connecting to the guest Wi-Fi network (VLAN 85, subnet $172.20.85.0/24$) are failing to access internet resources. Inspecting a network details page on an affected device reveals an IP address of $169.254.41.19$ with a subnet mask of $255.255.0.0$. Reviewing the DHCP server statistics shows that the active pool for VLAN 85 currently has $0$ available IP addresses remaining out of the $254$ allocated pool entries. Which of the following actions should the administrator take to resolve the root cause of this issue?

A network administrator is investigating a database connection issue on a host machine. The administrator needs to query the designated internal DNS server at $10.0.0.53$ directly for the record `db1.corp.internal` rather than relying on local resolver cache settings, and also inspect all active TCP socket connections along with listening ports on the local system. Which of the following command-line entries will successfully achieve these goals? (Select TWO)

During a fiber optic cabling deployment between two network racks, a technician notes high optical signal attenuation on a multi-mode fiber patch cord. The technician suspects a physical micro-fracture or excessive bend radius near one of the connector terminations where light is escaping through the buffer. Which tool should the technician use to visually locate the exact spot where light is leaking?

A network technician executes a command-line DNS query on a workstation to troubleshoot host resolution. The technician receives the following terminal output:

text
Server: resolver.lab.corp
Address: 192.168.1.254

Non-authoritative answer:
Name: fileserver.lab.corp
Address: 10.1.50.12

Which of the following statements correctly interprets the 'Non-authoritative answer' header in this CLI output?