Router Network Diagnostics Step

Network diagnosis is an important technical work which is good in management and good in network, and makes the network play the greatest role. In this paper, the layered diagnosis technique is introduced, and the diagnosis of router interface is discussed, and the troubleshooting of Internet connectivity Fault is summarized.

Overview of Network Fault diagnosis

Network fault diagnosis, starting from the phenomenon of fault, taking the network diagnostic tool as the means to obtain the diagnosis information, determine the network fault point, find the root cause of the problem, troubleshoot, and restore the normal operation of the network. Network failures are usually possible in the following ways: Physical layer

The failure of the equipment to connect with each other, the problems of the hardware and the circuit itself, the interface configuration problem of the network device in the data link layer, the Network Layer network protocol configuration or operation error, the device performance or communication congestion problem in the transport layer, three layer or network application error. The process of diagnosing network failures should go up from the physical layer along the OSI seven-layer model. First check the physical layer, then examine the data link layer, and so on, try to determine the failure point of communication failure until the system communication is normal.

Network Diagnostics can use a variety of tools: Router diagnostics commands, network management tools, and other troubleshooting tools, including LAN or WAN analyzers. Viewing the routing table is a good way to start looking for network failures. ICMP ping, trace commands, and Cisco Show commands, debug commands, are network tools to get useful information for troubleshooting. How to monitor the network under normal conditions of operation details and failure situation, what to monitor? The show interface command makes it easy to get information about each interface you want to check. The show buffer command provides a regular display of buffer size, usage, and usage conditions. The show proc command and show proc MEM commands can be used to track processor and memory usage. This data can be collected on a regular basis and used for diagnostic reference when a failure occurs.

Troubleshooting steps

The first step is to determine the specific phenomenon of the fault, and to analyze the type of cause of this failure phenomenon. For example, the host does not respond to customer request services. Possible causes of failure are host configuration issues, interface card failures, or the loss of router configuration commands.

The second step is to gather the information you need to help isolate the cause of the possible failure. Collect useful information from the network Management System, protocol analysis tracking, Router diagnostics command output report or software manual.

The third step, according to the collected situation to consider the possible causes of failure, to eliminate some of the causes of failure. For example, depending on the data you can troubleshoot a hardware problem, focus on the software reason.

The fourth step is to set up a diagnostic plan based on the last possible failure reason. Start the diagnostic activity with only one of the most probable causes of failure, which makes it easy to revert to the original state of the failure. If you consider multiple fault reasons at once, it is much more difficult to try to return to the original state of the failure.

The fifth step, the implementation of the diagnostic plan, carefully do every step of the test and observation, each change a parameter to confirm its results. The analysis results determine whether the problem is resolved, and if not, continue until the symptom disappears.

Network Layered Diagnosis Technology

The failure of physical layer is mainly manifested in the physical connection of the equipment, the connection cable is correct, Modem, CSU/DSU and other equipment configuration and operation is correct. The best way to determine whether a physical connection to a router port is intact is to use the show interface command to check the status of each port, interpret screen output information, view port status, protocol build status, and EIA status.

To find and troubleshoot the data link layer, you need to look at the configuration of the router and check the encapsulation of the same data link layer that the connection port is sharing. Each pair of interfaces has the same encapsulation as the other devices it communicates with. Check its encapsulation by looking at the configuration of the router, or use the show command to view the encapsulation of the corresponding interface.

The basic way to troubleshoot a network layer is to follow the path from source to destination, view the Router routing table, and check the IP address of the router interface. If the route does not appear in the routing table, you should check to determine whether the appropriate static route, default route, or dynamic route has been entered. Then manually configure some of the missing routes, or troubleshoot some of the dynamic routing processes, including RIP or IGRP routing protocol failures. For example, for IGRP routing, select information to Exchange data only between systems of the same autonomous system number (as) to see how the autonomous system number of the router configuration matches.