Network Troubleshooting

A network technician is troubleshooting a laptop that was moved from an executive office to a newly created conference room VLAN. The laptop cannot access internal resources, and executing `ipconfig /all` displays an IPv4 address of $169.254.88.15$ with a subnet mask of $255.255.0.0$. Which of the following statements correctly identify the cause of this issue and the appropriate next diagnostic step? (Select TWO.)

A network engineer is troubleshooting performance degradation on an enterprise Storage Area Network (SAN) uplink. After analyzing link metrics and performing diagnostic tests, the engineer successfully confirms their hypothesis that excessive frame errors are caused by an over-subscribed switch interface. Which of the following is the NEXT step the engineer should take according to the CompTIA troubleshooting methodology?

A network technician replaces a damaged modular plug on a Category 6 UTP cable. A basic continuity test shows that all eight conductors line up end-to-end, but the network link suffers from severe Near-End Crosstalk (NEXT) and high packet loss. Which physical cabling mistake is the most likely cause of this issue?

A network technician is troubleshooting an issue where a workstation fails to connect to an internal web application after a recent server migration. The technician executes two command-line utilities on the client workstation and receives the following output:

C:\> nslookup portal.company.local
Server: dns01.company.local
Address: 10.10.5.2

Name: portal.company.local
Address: 10.10.20.100

C:\> ping portal.company.local
Pinging portal.company.local [10.10.5.50] with 32 bytes of data:
Request timed out.

Based on the diagnostic output, which of the following is the most likely cause of this discrepancy?

A client workstation on VLAN 10 ($192.168.10.45/24$) cannot reach a database server located on VLAN 30 ($10.0.30.100/24$) across an enterprise Layer 3 switch with Access Control Lists (ACLs). Following the CompTIA network troubleshooting methodology, place the diagnostic and remediation actions in the correct sequential order from first step to last step.

A user's workstation is assigned the static IP address $192.168.10.45$ with a subnet mask of $255.255.255.0$ (/24). The user can successfully communicate with other devices on the local subnet, but cannot access any remote subnets or external websites. Running diagnostic checks shows that the workstation's default gateway is configured as $192.168.20.1$. Which of the following is the root cause of the gateway connectivity failure?

A network engineer provisions a new subinterface `GigabitEthernet0/0.40` on a branch router to serve an isolated IoT subnet ($172.16.40.0/24$). Devices connected to VLAN 40 are unable to reach external resources and auto-assign link-local IPv4 addresses in the $169.254.x.x$ range. A terminal capture on the router shows the following configuration:

text
interface GigabitEthernet0/0.10
description Corporate_Users
encapsulation dot1Q 10
ip address 172.16.10.1 255.255.255.0
ip helper-address 10.10.10.50
!
interface GigabitEthernet0/0.40
description IoT_Devices
encapsulation dot1Q 40
ip address 172.16.40.1 255.255.255.0

Existing client workstations on `GigabitEthernet0/0.10` receive leases dynamically from the central DHCP server at $10.10.10.50$ without issue. Which configuration change on the branch router will resolve the IP addressing failure for VLAN 40?

A network administrator has confirmed through diagnostic testing that an outdated firmware version on a core distribution switch caused intermittent BGP route flapping. Having confirmed this theory, the administrator is now preparing to execute the 'Establish a plan of action to resolve the problem and identify potential effects' step in the CompTIA troubleshooting methodology. Which of the following specific tasks should be conducted as part of this step? (Select TWO)

A network administrator is troubleshooting an issue where internal workstations on subnet $10.10.10.0/24$ cannot access a web server at $10.10.50.25/24$ using HTTPS. Upon inspecting the inbound Access Control List (ACL) on the destination interface, the administrator views the following configuration:

text
access-list 105 permit tcp 10.10.10.0 0.0.0.255 host 10.10.50.25 eq 80
access-list 105 deny ip any host 10.10.50.25
access-list 105 permit tcp 10.10.10.0 0.0.0.255 host 10.10.50.25 eq 443

Which of the following describes the root cause of the connection failure?

A network administrator is troubleshooting an issue where database servers deployed on a new broadcast domain (VLAN 104, $10.104.0.0/22$) fail to acquire dynamic IPv4 addresses and assign themselves $169.254.x.x$ addresses instead. A packet capture on the local router subinterface `GigabitEthernet0/0.104` shows incoming broadcast DHCP DISCOVER frames from clients, but no DHCP OFFER packets return. The central DHCP server is located on VLAN 10 ($10.10.10.2$). The configuration of the local subinterface is as follows:

interface GigabitEthernet0/0.104
encapsulation dot1Q 104
ip address 10.104.0.1 255.255.252.0

Which of the following actions should the network administrator perform to resolve this issue and enable dynamic address assignment for clients in VLAN 104? (Select TWO.)

A network administrator attempts to force Switch-B to become the primary Spanning Tree Protocol (STP) root bridge for VLAN 10 during an upcoming maintenance window. The administrator executes the CLI command `spanning-tree vlan 10 priority 61440` on Switch-B. After taking the existing core switch offline, host traffic experiences unexpected latency, and diagnostic logs reveal that Switch-C—which has a default configuration—was elected root bridge instead of Switch-B. Switch-C has an STP priority of 32768 for VLAN 10. Which of the following explains why Switch-C became the root bridge instead of Switch-B?

A network administrator is troubleshooting a client workstation that receives a name resolution error when attempting to reach an internal portal at `hrportal.contoso.com`. In what sequence should the administrator execute the following steps to systematically isolate the issue according to standard operating system name resolution precedence?

A network administrator is troubleshooting an issue where a client workstation cannot reach an internal database server located at $172.28.15.100$. The administrator collects the host settings and router interface details:

Host Settings:
- IP Address: $10.50.10.45$
- Subnet Mask: $255.255.255.192$ ($/26$)
- Default Gateway: $10.50.10.65$

Router Interface (GigabitEthernet0/0) & Inbound ACL:
- Interface IP: $10.50.10.1/26$
- Applied Inbound Access Control List:
- `line 10: permit tcp 10.50.10.0 0.0.0.63 host 172.28.15.100 eq 3306`
- `line 20: deny ip any any`

Which TWO of the following issues are directly preventing or obstructing successful communication and verification between the workstation and the database server?

A network technician is investigating intermittent connectivity and framing errors on a trunk link between two distribution switches. The technician has established a theory that a native VLAN mismatch is causing untagged traffic to drop and has confirmed this cause by inspecting packet captures on both switch interfaces. According to the CompTIA troubleshooting methodology, which of the following actions should the technician take NEXT?

A network administrator is troubleshooting an issue where an application host with IPv4 address $192.168.4.25/24$ cannot transmit HTTPS management data to a target server at $10.200.5.50/24$. Diagnostic tests reveal that the host can successfully ping its default gateway ($192.168.4.1$), but a traceroute to $10.200.5.50$ stops at $192.168.4.1$. Inspecting the gateway router shows the following configuration details:

text
ip route 10.200.5.0 255.255.255.0 192.168.4.1
access-list 105 permit udp host 192.168.4.25 host 10.200.5.50 eq 514

Which TWO of the following factors explain why HTTPS traffic (TCP port 443) fails to reach the destination? (Select TWO.)

A network technician is troubleshooting an intermittent 10GBASE-LR single-mode fiber optic backbone link between two core switches. Interface telemetry reveals elevated bit error rates (BER) and an optical receiver power level well below the specified threshold. Which TWO of the following diagnostic steps or tools should the technician use to isolate the physical layer defect?

A network technician is troubleshooting a wireless point-to-point bridge between two campus buildings situated 250 meters apart. Following a storm, maintenance crews re-anchored the directional antenna on Building B. Although there is a completely clear line of sight and transmit power settings remain unchanged on both units, the received signal strength indicator (RSSI) has dropped significantly from -58 dBm to -80 dBm. Inspection reveals that the antenna on Building A remains oriented with vertical polarization, whereas the antenna on Building B was reinstalled turned 90 degrees in horizontal polarization. Which of the following is the primary cause of the link degradation?

A network technician is investigating poor application throughput and significant packet loss on an enterprise host connected to switch interface FastEthernet 0/12. Output from the switch console reveals a high count of late collisions, frame check sequence (FCS) errors, and deferred transmissions on the port. A review of device settings shows that the host network interface card (NIC) was manually forced to 100 Mbps Full Duplex, while the connected switchport is configured with default auto-negotiation parameters. Which of the following best explains the root cause of this performance issue?

A network technician is troubleshooting an Ethernet connection in an office building and suspects that an unshielded twisted-pair (UTP) cable run inside a wall has been physically severed. Which hardware tool should the technician use to determine the exact distance along the cable to the location of the break?

A client computer configured with the IP address $10.0.1.25/24$ is unable to access resources on remote networks. An administrator inspects the IP configuration and discovers that the default gateway is set to $10.0.2.1$. Which TWO statements accurately describe the cause of this issue and the necessary resolution?