Network failure is inevitable, it is important to quickly isolate and troubleshoot. Network maintenance personnel should be equipped with corresponding tools and corresponding knowledge for timely, effectively, and solve problems. This article discusses ten ambiguous issues that network technicians and engineers often encounter. First analyze the problem, then discuss how tools use to help find and fail. It is designed to give a throwing jade.
Question 1: An abuse of the physical layer
- User complaint - can not log in or interrupt
- Symptom - only affecting a workstation, and the station is originally no problem
- Find the problem:
The cable terminal link is too long. Users move, bend, connect, and cut off network terminals (especially when laptops). Cheap cable testers can check this problem. Before you can say it is the problem of cable, you usually first consider the problem of cables. This requires a network test tool to prove whether the health status of the local network segment is good, whether the hub port function is normal, whether the network card and its driver work are good. Finally, check if there is a problem with the network interconnection device. Only when you know where you have problems with a problem with a problem with a problem, the disconnected connector or a ground loop should start testing the cable. In the copper-axis network, search for breaking between coaxial "T-head" and NIC cards, in the UTP network, continuously run the instrument graph test function, and the terminal is constantly moving to identify contact or short circuit.
-Solve the problem:
Replace the workstation connection cable, replace the damaged connector, or stop using the horizontal cable. Take a completely check the processed cable again.
Question 2: Quick Ethernet than the Ethernet before the upgrade is slow
User complaining -10Mbps Ethernet speed slowly, upgrade to 100Mbps Fast Ethernet and even unable to connect the Internet.
- Symptom - A workstation that affects the new workstation or upgrade.
- Find the problem:
For the UTP5 non-shielded twisted pair, the cable tester is tested whether it meets the EIA / TIA-TSB67 standard corresponding to 100 Mbps transmission rate. Certain cable links working in 10Mbps Ethernet work are not working properly because the proximal crosstalk is too large at 100Mbps Ethernet. The signal is coupled to the neighboring line to cause high frequency signal transmission failure. The line of UTP is separated and even makes the network to be paralyzed at a certain flow.
-Solve the problem:
Replace or deactivate the links that cannot be connected, the fault is cleared and then all the links placed at the time.
Question 3: Invalid watchdog
- User complaint - NetWare remote server that cannot connect to Novell network
- Symptom - affect all workstations connected to the server within this network segment
- Find the problem:
Check the health of the network segment, pay attention to observe the utilization rate, collision, error frame, and broadcast frame level. At this point, a large number of collisions or error frames can be observed, the collision or error frame can cause a delay in the "Hello" frame between the client and the server. Repeat this test with the remote network segment where a specified server is located. If both network segments appear blank, use the Network Tester to query the SNMP proxy in the router, check the routing table between the two network segments. Determine that there is no crowding problem. In order to effectively use resources, the Novell server cancels the client if the client does not respond to the "Hello" frame within the time allowed by the watchdog.
-Solve the problem:
When you simply change the watchdog, the delay parameters are changed, and the parameters in the Novell server are changed. If the situation is improved, it can be determined as a cause of the frame loss, correct the parameters of the watchdog delay frame timer.
Question 4: Ranyi Chain Effect - User Complament - Network Service Slow - Symptom - All users of an Ethernet segment. Network service (access server) is slow, but it is independent of a server connected. - Find problems: Enter the network tester into the hub in the peak hours, running network health status test. A large amount of error frame will be observed. In the 10BASE-2 network, the type of error frame is classified as "delay collision". In the 10BASE-T network, the type of frame error is classified as a typical framework element sequence error (FCS error), with the growth of network users, 黾 黾 ǔ 朐 в в в в в в в α α α α в α α α α α α α α α α α α α α α α α α α α α α α α α α α α ? / P> - Solve the problem: Statistically the number of repeaters passing between two network devices. There should be more than 4 in 10Mbps Ethernet, and there should be no more than 2 in 100Mbps Fast Ethernet. If the quantity exceeds the standard, the network topology is corrected according to the Ethernet standard, and then the error frame has appeared. Question 5 - Network Manager's Retribution - User Complament - A workstation gap error, can not log in or cannot access remote server - symptoms - only affecting a workstation, this problem is usually increasing, mobile, changing workstations, and this problem: First eliminate the potential problem with your users with accounts and security settings. Let the user log in and try to repeat this operation from another workstation. If successful, you can use the network tester from the link status between the user to the server. Then test the network card, detect the functions and conditions of the hardware and drivers. If there is no problem, check the IP settings, determine if the user's IP address is valid or has a duplicate IP address. Determine whether the subnet mask of this network segment and whether the default address of the router is correct, the DNS server (if any) is dedicated. If the IP address of a new workstation is repeated with the IP address of the print server, each person's printing will point to the new client. - Solution: Change to the right setting, then restart the workstation problem 6: Fiber Optical Illusion - User complaint - Slow - Slow - Symptoms of the entire network - Find problems: In normal network use time, The network tester is connected to the hub and flows traffic at both ends of the fiber connection. Disconnect or attach the optical fiber at a certain moment, and whenever the fiber is connected to the network segment, a large amount of error frame is observed. Inferior fiber link connectivity generates a large amount of garbage frame in its subsidized segment, forcing the workstation to rehabilize the frame, the network speed slows down. - Solve problems: Clean or reinstall fiber optic connector, reset all connector, check the network health again, and only a small amount of error frame should be used. Question 7: Strange! Is the cable hit at night? - User complaint - can not connect to the Internet or not login - symptoms - only one work station on the network segment can be online - find the problem disconnect the workstation connection cable, connect the network tester, not to detect the connection signal from the hub. Run the cable test to see if the cable from the office to the wiring is open. If not normal, set the tool in the audio generator position, from the wiring audio detector to the cable corresponding to the office, usually, the cable clue will be pushed and collided with changes in the wiring. Causes the connector to fall off or loose. - Resolve the problem: Reissue the cable connector between workstations and workstations and hubs to see if the connection signal indicator is lit and determine if the user can access the Internet. Question 8: Is the heart of "patient" is still jumping? - User complaining - the speed of the network busy peak visits is very slow - symptom - All workstations of individual network segments have no response to the server of this network segment or other network segments. - Find Problem: Connect the Network Tester to the network segment during peak hours.
