Network Troubleshooting缩略图

Network Troubleshooting

In the process of resolving network issues It is essential to be aware of the OSI models in mind. You must begin by working your way to the layer of physical up to the layer of application. This approach from the bottom helps solve network issues successfully because each layer depends on the previous layer for proper operation. This article will present an overview of how to troubleshoot problems in the three initial levels in OSI. OSI model. Troubleshooting the Physical Layer (Layer 1) The physical layer comprises everything that produces and moves bits from point A to B. This is known as the network interface layer that includes Ethernet as well as WiFi cards as well as fiber cables and air that allows computer hosts and hosts to connect with other hosts and with the outside world at large. To resolve issues with this layer, a network engineer should utilize the diagnostic tools the manufacturers include on their devices. For Ethernet cards, the basic diagnostic commands provide information about the duplex and speed of link that the card has established on the other end of the connection. For the case of a WiFi adapter program will be able to report the strength of the signal and connectivity quality that was established by the station that is in use. This information is essential in determining how reliable the Layer 1 connection established. To resolve issues using fiber or copper cables you can make use of an optical reflective time-domain device (TDR) and optical time-domain reflectometer in case of fiber links. Certain networking companies also have a the basic TDR function in their equipment. For Wi-Fi networks spectrum analyzers can be helpful to give information about “the air” and detect any possible interferences from the environment like microwave ovens. It is possible to contact suppliers like MetaGeek and Ekahau in search of these solutions. Troubleshooting the Data-Link Layer (Layer 2) To identify the data-link-layer issues Network engineers can use an switches command line and examine the MAC address table. This gives information on the MAC addresses discovered on switched ports. To investigate issues with Layer 2 communications between hosts engineers from network can utilize methods of analysis that are passive, like wireshark that is GUI and based on tcpdump that is a command line-based. The tools allow for the recording of frames that flow across networks, switches or host. One of the most important things to remember when tackling issues with layer 2 is the spanning tree. Spanning tree is an Layer 2 technology that allows switched networks to create an unloop-free topology. This occurs when redundancy is introduced in a network’s design. If a topology of a network has loops, the frames move throughout the network without ever reaching their host of destination or being discarded creating broadcast storms. Broadcast storms can saturate links and can cause unstable CAT (Content addressable table) of switch. Spawning tree prevents this situation by removing switches that create loops. For spanning tree to work properly for optimal performance, all switches on the network should be correctly set up. Being familiar with the spanning tree and diagnostic commands for switches is an essential understanding for troubleshooting network issues. Troubleshooting the Network Layer (Layer 3) The most frequently used commands used to resolve layer 3 issues are the ping or traceroute. With ping , you can check the possibility of a host connecting to the network that is its destination or. Traceroute allows you to discover the hops that can be used to route to a host that is destined for destination. If you are trying to solve problems with layer 3 is important to determine whether the host that you want to connect to is within your company or not. If it is, the problem-solving efforts are aimed at finding out if an issue with the configuration of your network or something else causes problems with connectivity or performance. If at the opposite end the network path that leads to the destination host is traversed by an outside party, it’s crucial to supply sufficient details and demonstrate that it’s not the fault of someone else. In one way or another both traceroute and ping are two useful commands that provide insight into the reachability and performance issues that exist in between IP hosts. Closing remarks If you are trying to resolve issues with performance of your network it is essential to remember that you are working with the OSI models and the layers. Beginning with the lowest layers and then moving up will ensure you are using the right troubleshooting techniques will yield faster resolution.

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