Local area networks (LAN) are integral to the operation of many businesses today. The most common LANs use Ethernet, a data link layer protocol, and Internet Protocol (IP), a network layer protocol.
A LAN is comprised of many elements: printers, monitors, PCs, IP phones, servers, storage hardware, networking equipment, security software, network applications, enterprise applications, office productivity applications, and more. Devices on the network are linked physically by twisted pair copper, fiber or wireless access points.
Troubleshooting LANs is typically the job for the frontline network support staff - engineers and technicians. Common problems include user connection issues and slow networks.
Root causes of LAN problems are frequently caused by one of these three sources:
1. Physical layer: copper, fiber or wirelessPossible causes:
- Damaged or dirty cabling or terminations
- Excessive signal attenuation
- Insufficient cable bandwidth
- Wireless interference
2. Network Layer: Ethernet and IPPossible causes:
- Damaged networking devices
- Incorrect or sub-optimal device configurations
- Authentication and association issues
- Insufficient network bandwidth
3. Switches and VLANs Possible causes:
- Excessive utilization
- Too many errors
- Incorrectly assigned VLAN membership
- Traffic priority (CoS/QoS) issues
Best practices for successful LAN troubleshooting include these steps:
1. Identify the exact issue or problem: Have the person who reported the problem explain how normal operation appears, and then demonstrate the perceived problem.
2. Recreate the problem if possible: Ask yourself if you understand the symptoms, and verify the reported problem yourself if possible.
3. Localize and isolate the cause: Attempt to isolate the problem to a single device, connection, or software application.
4. Formulate a plan for solving the problem: Research and/or consider the possible solutions to the problem. Consider the possibility that some solutions to the problem at hand may introduce other problems.
5. Implement the plan: Your actual solution to the problem may be replacing hardware, implementing a software patch, reinstalling the application or component or cleaning a virus infected file. If the problem is the user account, the user’s security settings or logon scripts may need to be adjusted.
6. Test to verify that the problem has been resolved: After you have implemented the solution, ensure that the entire problem has been resolved by having the user