Open Impedance Mismatch (Echo)
Any network segment can consist of a single continuous section of cable or be constructed from multiple cable sections attached through switches and other hardware. If multiple cable sections are used, it can result in impedance mismatches caused by slight differences in the impedance of each cable section. Impedance refers to the total opposition a circuit or device offers to the flow of a signal, measured in ohms. All media, such as twisted-pair cable, has characteristic impedance. Impedance characteristics for twisted-pair cable include 100, 120, and 150 ohms. UTP typically has an impedance of 100 ohms, and STP has an impedance of 150 ohms. Mixing these two wires in the same cable link can result in an impedance mismatch, which can cause the link to fail. To help prevent impedance mismatch, use cable rated with the same impedance rating.
Shorts
Electrical shorts can occur in any type of cable that has electrical current flowing through it. Shorts occur when the electrical current travels along a different path than what is intended. This can often happen if a network cable is not made correctly and wires are touching each other, improperly grounded, or touching metal. This is another reason to be careful when attaching your own RJ-45 connectors to twisted-pair cable. Sometimes, network cables can become damaged, bent, or mishandled, and shorts can occur. Copper-based media that carries electrical current is susceptible to shorts; wireless and fiber optic cable are not.
In this tutorial:
- Troubleshooting Procedures
- The Art of Troubleshooting
- Troubleshooting Servers and Workstations
- General Troubleshooting Considerations
- Troubleshooting Methods and Procedures
- Step 1: Information Gathering-Identify Symptoms and Problems
- Information from the Computer
- Information from the User
- Step 2: Identify the Affected Areas of the Network
- Step 3: Determine if Anything Has Changed
- Changes to the Network
- Changes to the Server
- Changes to the Workstation
- Step 4: Establish the Most Probable Cause
- Step 5: Determine if Escalation Is Necessary
- Step 6: Create an Action Plan and Solution Identifying Potential Effects
- Step 7: Implement and Test the Solution
- Step 8: Identify the Results and Effects of the Solution
- Step 9: Document the Solution and the Entire Process
- Troubleshooting the Network
- Where the Cable Is Used
- Crosstalk
- Open Impedance Mismatch (Echo)
- Managing Collisions
- Troubleshooting Infrastructure Hardware
- Configuring and Troubleshooting Client Connectivity
- Troubleshooting Incorrect VLANs
- Identifying Issues That Might Need Escalation
- Troubleshooting Wireless Issues
- Troubleshooting Wireless Signals
- Troubleshooting Wireless Configurations