Network Troubleshooting

A network administrator is troubleshooting an issue where users are unable to access a secure website hosted on an internal Linux server. The administrator executes the command `netstat -an` on the server and receives the following output snippet:

text Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN

Based on this output, which of the following is the primary cause of the connectivity failure?

A network technician is troubleshooting connectivity issues following a switch maintenance window. Workstations assigned to VLAN 45 on an edge switch can no longer communicate with the default gateway hosted on the core switch, whereas hosts on VLAN 10 attached to the same edge switch maintain uninterrupted access. The trunk link between the switches is configured using 802.1Q. Output from `show interfaces trunk` on the core switch shows the allowed VLAN list on interface GigabitEthernet0/1 is set to `10,20,30`. Which of the following configuration changes on the core switch will resolve the connectivity issue for VLAN 45?

A network technician is troubleshooting an issue where a newly connected workstation on VLAN 30 fails to receive an IP address from a central DHCP server located on VLAN 10. Place the troubleshooting steps in the correct logical sequence according to standard network troubleshooting methodology to isolate and resolve the issue.

A network technician is troubleshooting a client workstation that cannot access an internal web portal by its fully qualified domain name (FQDN). Following a standard bottom-up troubleshooting workflow to isolate network issues from local network configuration to name resolution, place the following command-line steps in the correct logical diagnostic sequence.

A network administrator is troubleshooting an issue where workstation users are directed to an old server IP address for an internal web application hosted at `app.corp.internal`. The administrator suspects the local DNS server (`192.168.1.1`) is returning a cached, non-authoritative record. Which command should the administrator run to query the authoritative DNS server at `10.100.1.10` directly for the IPv4 address record?

A network administrator is setting up a new server on a subnet designed for database hosts: $172.16.10.128/26$. The default gateway router interface for this subnet is assigned IP address $172.16.10.129/26$. The administrator manually configures the server with IP address $172.16.10.66$ and subnet mask $255.255.255.192$ ($/26$). Upon testing, the server cannot ping its default gateway or reach any external networks. Which of the following best identifies the root cause of this connectivity failure?

A network administrator connects two enterprise switches via a fiber trunk link on interface GigabitEthernet 0/1. Shortly after enabling the link, console logs on both switches begin displaying periodic warning messages indicating a native VLAN mismatch. Interface status shows the trunk link is active, but untagged management traffic sent from VLAN 10 on Switch-A is being improperly received on VLAN 20 by Switch-B. Which of the following configuration changes will resolve this issue while restoring proper 802.1Q trunking functionality?

Match each switch status indicator or log message on the left with its corresponding underlying root cause on the right.

A network administrator installs a new 10Gbps LC duplex fiber patch cable between two core switches using matching SFP+ transceivers. After plugging in the cable, the link status LEDs on both switch interfaces remain completely dark. Testing with a visual fault locator (VFL) confirms light is passing through both fiber strands with no physical breaks. Which of the following is the most appropriate troubleshooting action to resolve this issue?

A network technician is conducting diagnostic tests on a newly deployed workstation. Match each command-line utility command to its correct network troubleshooting function or operational output.

A network administrator is troubleshooting network connectivity issues for automated guided vehicles (AGVs) deployed on a newly provisioned warehouse floor subnet (VLAN 45: $10.45.0.0/23$). The AGVs cannot communicate with the central controller on another subnet. Inspecting the IP configuration on an AGV displays the following terminal output:

IPv4 Address. . . . . . . . . . . : 169.254.12.88
Subnet Mask . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . :

The central DHCP server is located on VLAN 10 ($10.10.0.50$) with a valid, unexhausted scope for VLAN 45. Which TWO of the following statements correctly identify the underlying cause and the required resolution?

An infrastructure team is auditing an 802.1Q trunk connection between Switch-1 and Switch-2 on interface FastEthernet 0/24. Syslog on Switch-1 displays `%CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on FastEthernet0/24 (1), with Switch-2 FastEthernet0/24 (30)`. Additionally, hosts assigned to VLAN 30 on Switch-1 cannot reach resources on VLAN 30 attached to Switch-2. A check of Switch-1 interface FastEthernet 0/24 shows that its trunk allowed VLAN list currently includes only VLANs 10 and 20. Which TWO of the following configuration steps must be performed on Switch-1 to resolve the native VLAN warning and allow VLAN 30 traffic to traverse the link? (Select TWO.)

A network technician needs to pinpoint the precise location of a conductor break in a 90-meter Category 6 UTP cable run hidden behind drywall. A basic wire mapper confirms an open circuit on pin 3, but cannot determine how far along the cable the fault occurred. Which diagnostic tool should the technician use to measure the exact distance to the cable break?

A network administrator configures a new DHCP scope on a centralized server to service clients on VLAN 20 (subnet $10.20.10.0/24$). Users on VLAN 20 report that they can successfully communicate with other local hosts on VLAN 20, but cannot access external networks or corporate servers located on other subnets. Running `ipconfig /all` on an affected client displays an IPv4 address of $10.20.10.45$ with a subnet mask of $255.255.255.0$, but the Default Gateway field is empty. Which of the following is the most likely cause of this issue?

A network engineer is troubleshooting a newly installed multi-strand MPO/MTP multimode fiber trunk cable connected between two high-density distribution switches. Although transceivers are installed and powered, the link status remains down, and switch logs indicate insufficient optical power reception. Which of the following diagnostic steps or corrective actions should the engineer take to resolve this physical layer issue? (Select TWO.)

A network administrator is troubleshooting severe performance degradation on an enterprise network segment. Users report extreme file transfer delays when communicating with a local server connected to interface GigabitEthernet 0/5 on Switch-SW1. Interface metrics on Switch-SW1 reveal a rising count of late collisions, frame check sequence (FCS) errors, and alignment errors, despite low overall bandwidth utilization. Further inspection shows the server's network adapter is manually configured for 1000 Mbps Full-Duplex, whereas the connected switch port is set to auto-negotiation. Which of the following accounts for the root cause of this issue?

A network administrator installs a multimode fiber optic patch cable between two rack-mounted switches in a data center. Although physical link connectivity is established, the switch management interface logs a high rate of bit errors and optical power loss. An OTDR scan reveals a sudden, localized non-reflective loss at a point where the cable is tightly zip-tied around a sharp corner of the cable tray, with no glass break detected. Which of the following physical layer issues is the most likely cause of this signal degradation?

A network administrator is diagnosing several switching, trunking, and physical layer issues across access and core switches in an enterprise environment. Match each switch console symptom or log output on the left with its corresponding underlying root cause on the right.

A network technician is responding to a user ticket reporting a duplicate IP address error notification on VLAN 12 ($10.12.0.0/24$). Place the following diagnostic and remediation steps in the correct chronological order from initial investigation to final resolution.

A network administrator is troubleshooting connectivity to an internal updates repository on a Windows workstation. The workstation is failing to resolve the host name update.service.internal. To resolve the issue, the administrator wants to purge any cached domain name resolution records locally on the workstation and directly test hostname resolution using a specific internal DNS server located at 192.168.10.50. Which of the following commands should the administrator execute to accomplish these tasks? (Select TWO)