Not sure where to begin? The easiest place is to start at the bottom and work your way through the layers. Over the next few months, our EYE newsletter will feature some tips from NI University instructor Mike Motta – who helps educate countless individuals throughout the year on properly maintaining their network. In this article, we'll look at locating and diagnosing physical-layer issues in 6 steps.
Best Practice Note: Before troubleshooting, make sure you have a good network map showing how everything is connected through ports and switches. This allows you to know which switch and port interfaces to review for errors.
1. Ping the device
Ping the end device 5 times to verify connectivity between the console and device. If you're unable to successfully ping, it means the device is generating some type of error condition. If you can ping, everything is correctly connected to the network.
2. Verify switch connections
If you receive errors during pinging, the next step is to check the switch connections using the Show Interface command detailed in the Tech Spotlight section. Check switches and ports for errors and identify which side of the conversation is causing the problem. Verify the cable is correct for the network (Category 5 or higher for 10/100/1000 Gigabit) and doesn't exceed maximum distance requirements. Check the link status and be sure the port is enabled, operational, and configured appropriately.
3. Verify transceiver module
Before contacting the device manufacturer for support, be sure that you have the appropriate SFPs for the device.
4. Investigate errors
Within the Privileged Exec mode with Cisco switches, you can verify errors using the Show Interface command. Identify the port is enabled, duplex and speed settings are correct, and whether auto-negotiate is set. Although Show Interface is a Cisco command, other switches have similar commands to display status and configuration.
5. Switch checklist
If you are using multiple switches, make sure all are running the same IOS version. Verify interfaces are operational and configured properly. On Cisco switches, run the Show CDP Neighbor Details command to discover neighbor devices attached to the specific switch and verify connectivity between all other Cisco devices.
6. Attempt to ping device
Assuming everything is properly connected, you should be able to successfully ping all attached devices. With everything correctly connected at the physical layer, the next step will be to analyze communications and application performance using Observer's Expert Analysis.
Use the Network Application Performance white paper to walk through Observer's expert analysis capabilities for analyzing and troubleshooting application performance and transactions. In addition, to sharpen your network management and troubleshooting skills, sign up for one of our Network Instruments University classes.
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