Network Troubleshooting

Match each physical or protocol network troubleshooting scenario to the most appropriate diagnostic tool or analyzer function.

A network administrator is troubleshooting persistent link degradation and high CRC error counts on a 75-meter Category 6 UTP run connecting an industrial factory floor workstation to an IDF switch. A basic continuity wire mapper indicates that all eight conductors are mapped correctly according to TIA/EIA 568B pinouts at both ends. Which of the following diagnostic steps or corrective actions should the technician take to isolate and resolve the physical layer failure? (Select TWO.)

A network technician is troubleshooting a client workstation that is generating an APIPA address ($169.254.x.x$) on a newly created VLAN. Which sequence of diagnostic steps represents the correct order to isolate and resolve this DHCP relay issue?

A system administrator is troubleshooting a database connection failure from a newly deployed application host (`10.150.12.45/24`) to an enterprise database server (`172.28.100.50`). The application requires TCP port 5432 (PostgreSQL). The administrator executes diagnostic commands on the host and the intermediary router:

Host CLI Output (`ip route` & `ip addr`):
text eth0: inet 10.150.12.45/24 brd 10.150.12.255 scope global eth0 default via 10.150.13.1 dev eth0

Router ACL Output (`show ip access-lists OUTBOUND_DB`):
text Extended IP access list OUTBOUND_DB 10 permit tcp 10.150.12.0 0.0.0.255 host 172.28.100.50 eq 3306 20 deny ip any any

Based on the diagnostic output, which TWO factors are directly preventing the application host from communicating with the database server?

A network administrator is investigating severe transmission errors and dropped frames on a newly installed Category 6 UTP cable connecting a core switch to a critical server. The administrator must verify whether the copper cable installation meets official TIA/EIA structural performance standards, including measuring Near-End Crosstalk (NEXT), return loss, and attenuation under high-frequency signal loads. Which diagnostic tool should the administrator use to perform this compliance verification?

A network administrator is troubleshooting connectivity issues on a Linux backup server. The server is assigned the static IP address $172.16.88.200/25$. Local diagnostic testing reveals that the server can communicate with hosts on its immediate local network segment, but traffic destined for remote subnets fails completely. The administrator verifies the host routing table output:

text
default via 172.16.88.1 dev eth0
172.16.88.128/25 dev eth0 proto kernel scope link src 172.16.88.200

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

A network administrator is investigating a connectivity issue on a newly deployed workstation on the finance floor. The user reports being able to communicate with other devices on the local subnet, but cannot access external services or the internet. The administrator runs `ipconfig /all` on the client machine and observes the following output:

IPv4 Address . . . . . . . . . . . : $10.45.20.115$
Subnet Mask . . . . . . . . . . . . : $255.255.255.0$
Default Gateway . . . . . . . . . . : $10.45.21.1$
DHCP Server . . . . . . . . . . . . : $10.45.10.15$

Which of the following identifies the root cause of the workstation's external connectivity failure?

Match each command-line network utility invocation to its primary operational purpose during a network diagnostic workflow.

A network technician is migrating a branch office segment to a new IPv4 addressing scheme ($10.50.40.0/24$). Workstations on VLAN 40 successfully acquire IP addresses from the central DHCP server, but users report they cannot reach servers on other subnets or access the internet. An output inspection of `ipconfig /all` on an affected client displays the following parameters:

- IPv4 Address: $10.50.40.88$
- Subnet Mask: $255.255.255.0$
- Default Gateway: $10.50.4.1$
- DHCP Server: $10.20.10.5$

Which TWO of the following configuration changes are required to restore full routing capabilities for these workstations?

A network technician needs to determine which port on a busy 48-port patch panel connects to an unlabeled wall outlet in a newly renovated conference room. Which hardware troubleshooting tool should the technician connect to the outlet to trace the physical cable run back to the correct patch panel port?

Users on a newly provisioned branch office subnet ($172.16.40.0/24$) report an inability to reach intranet services or external websites. Running `ipconfig /all` on an affected client workstation yields the following output:

IPv4 Address. . . . . . . . . . . : 169.254.14.88
Subnet Mask . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . :
DHCP Server . . . . . . . . . . . :

The central DHCP server is located on the headquarters data center VLAN ($192.168.10.0/24$). Network operations confirms that the DHCP scope for $172.16.40.0/24$ is online and contains 150 available IP addresses. Which of the following is the most likely root cause of this issue?

A network administrator is troubleshooting an issue where a workstation attached to Switch-A on port FastEthernet 0/5 experiences severe latency and dropped frames during file transfers to a server in the same VLAN on Switch-B. Switch-A logs indicate frequent speed and duplex mismatch alerts, and interface counters show a high count of late collisions on FastEthernet 0/5. Physical cable testing verifies the cabling is intact. The workstation's network interface is manually configured for 100 Mbps Full Duplex, whereas the switch port is set to auto-negotiation. Which of the following is the root cause of the performance degradation and frame loss on this link?

A network administrator is investigating an issue where a client workstation ($10.20.40.15$) fails to connect to an internal web service running on port $8080$ at $10.20.40.250$. The administrator executes two command-line diagnostic utilities from the workstation, producing the following terminal outputs:

Command 1: `ping 10.20.40.250`

Pinging 10.20.40.250 with 32 bytes of data:
Reply from 10.20.40.250: bytes=32 time=2ms TTL=64
Reply from 10.20.40.250: bytes=32 time=1ms TTL=64

Command 2: `tracert -d 10.20.40.250`

Tracing route to 10.20.40.250 over a maximum of 30 hops
1 <1 ms <1 ms <1 ms 10.20.40.250
Trace complete.

Based on these diagnostic results, which TWO of the following conclusions are valid? (Select TWO.)

A network technician is troubleshooting a newly installed Category 6 UTP cable drop connecting a desktop computer to a wall outlet. The workstation successfully connects at 100 Mbps Fast Ethernet, but fails to establish a 1000BASE-T (Gigabit Ethernet) link. A basic wiremap continuity tester indicates that all eight conductor pins match correctly end-to-end (pins 1 through 8 are straight-through). Which of the following diagnostic findings or testing methods would most likely identify the root cause of this failure? (Select TWO)

Match each network troubleshooting scenario to the most appropriate hardware diagnostic tool or packet analyzer feature.

A network engineer is investigating excessive link degradation and packet loss on a 10GBASE-LR single-mode fiber link connecting two campus buildings spaced 1.2 kilometers apart. An optical power meter confirms that received optical power is 16 dB below expected baseline levels, indicating high attenuation along the path. Which diagnostic tool should the engineer use to identify the precise distance to the macrobend or splice fault causing the signal loss?

A network technician is troubleshooting an IP surveillance camera connected via an 80-meter Category 6 Ethernet drop. Although basic wiremap testing confirms all eight conductors have pin-to-pin continuity with no opens or shorts, the camera regularly experiences frame drops and fails to negotiate a 1000Base-T link, falling back to 100Mbps. The technician suspects high signal degradation and Near-End Crosstalk (NEXT) caused by excessive untwisting of wire pairs near the patch panel punch-down termination. Which of the following tools should the technician use to perform a full frequency performance analysis and verify whether the cable run complies with Category 6 standards?

A network technician configures an 802.1Q trunk link between Switch-1 and Switch-2. Switch-1 is configured with native VLAN 10, whereas Switch-2 is configured with native VLAN 20. Users connected to VLAN 10 on Switch-1 report that they can unexpectedly reach servers on VLAN 20 attached to Switch-2 without going through a router, while console logs generate periodic CDP error messages. Which of the following best explains the root cause of this cross-VLAN communication?

Match each network physical layer diagnostic tool with the troubleshooting scenario it is best suited to resolve.

A network technician executes `nslookup -type=TXT _dmarc.example.com` to verify an email authentication policy record. The command returns the following terminal output:

Server: UnKnown
Address: 192.168.1.2

Non-authoritative answer:
_dmarc.example.com text = "v=DMARC1; p=reject;"

Based on this command-line output, which of the following statements correctly interprets the diagnostic result?