Question

Difficulty: HardUtilizing Hardware Testers and Packet Analyzers

A network administrator is investigating intermittent performance issues on a database server connected to a distribution switch via a multi-mode fiber optic trunk. System logs reveal high physical-layer frame error counts as well as unexpected database session terminations. Which TWO diagnostic actions should the administrator take to accurately pinpoint the physical cable fault and analyze the session disruptions?

  1. Connect an Optical Time-Domain Reflectometer (OTDR) to the fiber run to measure signal attenuation and identify the exact distance to any physical breaks or excessive splices.Answer
  2. B
    Attach a copper Time-Domain Reflectometer (TDR) to the fiber patch panel to locate impedance mismatches along the optical strand.
  3. Use a packet analyzer with a display filter isolating TCP RST flags and TCP retransmissions to analyze connection teardowns.Answer
  4. D
    Configure a packet analyzer capture filter for UDP port 80 to detect Layer 2 Ethernet framing errors occurring on the physical interface.

Answer

The correct diagnostic actions are using an Optical Time-Domain Reflectometer (OTDR) to locate physical fiber defects and configuring a packet analyzer display filter for TCP RST flags and retransmissions to evaluate session terminations.
The correct diagnostic steps involve applying an Optical Time-Domain Reflectometer (OTDR) to analyze light reflections and locate physical defects along the multi-mode fiber run, alongside employing a packet analyzer configured with TCP control flag filters (such as TCP RST and retransmission markers) to trace transport-layer session terminations.

Step-by-Step Solution

1
Identify the physical medium and select the appropriate hardware testing device.
Since the uplink utilizes multi-mode fiber optic cabling, an Optical Time-Domain Reflectometer (OTDR) must be selected rather than a metallic/copper TDR.
OTDRs specifically analyze optical attenuation, backscatter, and distance to faults in fiber optic cables.
2
Select the appropriate software analysis tool and protocol filter for troubleshooting transport layer session terminations.
Configure a packet analyzer (such as Wireshark or tcpdump) with a filter focused on TCP control flags (specifically TCP RST) and retransmissions.
Database connection terminations operating over connection-oriented TCP emit RST or FIN packets when abnormally severed, which are captured at Layer 4.

Key Concept

Selecting media-appropriate hardware testers (OTDR for fiber optic reflection analysis) and configuring transport-layer packet capture filters for session troubleshooting.
Estimated Time:2m 0s
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