【 Weak current College 】 common switch failure categories and troubleshooting steps

In the larger local area network, often encounter network channel is serious plug phenomenon, the symptoms of causes, such as network suffered a virus attack, hardware damage to network devices, network ports appear transmission bottlenecks. However, from the network plug phenomenon of statistical probability, the network had alterations or changes of location most prone to failure phenomenon because of frequent changes to the network can easily cause network loops, and caused by a network loop network plug phenomenon often have strong anonymity is not conducive to the efficient removal of symptoms. So we can find a suitable solution to efficiently resolve network loops caused by network channel plug phenomenon? actually, clever configuration switch loopback monitoring function, we can quickly determine if there is a network in LAN loops, then caused by network loops and the symptom can be quickly solved!

Judge the ideas network loops

Because now the new buying back almost all support the switch port loopback monitoring function, ingenious use of this feature, we can make the switch automatically determining the specifies the communications port for the network loops occur. Once we specify Ethernet communication port loopback monitoring feature is enabled on the switch device can automatically scheduled on all communication port scan monitoring so that judgment communication port for network loop phenomenon. If the monitor to a switching ports are network loopback, the switching ports automatically in loopback monitoring State, in accordance with Exchange port parameter settings and the port, it switches automatically to the specified Exchange port closed off or auto-escalation of log information corresponding to the port, we only need to view logging information or under port enabled, you can quickly determine if there is a network in LAN loop phenomenon. Now, this article to H3CS3050 model switches the blueprint for action, to give you a detailed look at using loopback monitoring function to determine the specific network loop phenomenon configuration steps.

Enable port loopback monitoring

In order to be able to make the switch automatically determining the local LAN network loop phenomenon exists, we need to enable the switch port loopback monitoring capabilities, while also enabling port loopback monitoring managed features, but by default, these features are turned off, we need to manually configure the switch to switch specifies port loopback monitoring capabilities, and the port loopback monitoring managed functions enabled.

In the enabled switch port loopback monitoring function, we can start with system administrator permissions on the remote login into the admin interface, switch the interface to the command line prompt string command "sys", click the Enter key will switch over to system view status; then in the system view, do one of the string command "loopback-detectionenable", this switch global port loopback monitoring function has been successfully enabled.

Below, we also need to switch to specify the Ethernet switch port loopback monitoring feature is enabled; for example, if we want to make Ethernet 16-port loopback monitoring feature is enabled, you can switch the view state of the system, enter the string command "interfaceGigabitEthernet1/0/16", click the Enter key, the interactive machine configuration state will enter Ethernet 16-port, switch the view state of the command prompt also automatically become "H3C-GigabitEthernet1/0/16," in the command line prompt string command executed again "loopback-detectionenable", the Ethernet switch 16 port loopback monitoring function has been successfully enabled;

Next, we also need Ethernet 16 port view state enabled Hybrid ports and Trunk port network loopback monitoring managed function, when you enable this feature, we only need the "H3C-GigabitEthernet1/0/16" command line prompt, execute the command "loopback-detectioncontrolenable" string.

On a different VLAN loopback monitoring

Through the above configuration, switch system can only specify the Ethernet ports of Hybrid ports and Trunk port is a member of the default VLAN implementation network loopback monitoring operation, but cannot execute other VLAN, automatic monitoring operation so that the work of other virtual local area network subnets if there are network loops, switch still cannot automatically determine. To do this we need with the appropriate settings to switch the system to the other VLAN can automate network loopback monitoring operations; for example, for Ethernet switch 16 port of Hybrid ports and Trunk ports are located in the execution of all VLAN network loopback monitoring operations, you must make the following configuration:

First of all, will switch over to system view state, after the entry into the Ethernet port on a view, in 16 "H3C-GigabitEthernet1/0/16" command line prompt, enter the string command "loopback-detectionper-vlanenable", click the Enter key, the system will switch to Hybrid ports and Trunk ports are located in the execution of all VLAN network loopback monitoring operations.

Of course, all strings in the above commands will be executed succeeds, we also need to "quit" command to exit the switch system view state before executing the "save" command switch port configuration parameters saved before it can be, otherwise the switch will restart once, before the various configuration is automatically lostLost.

Control network loopback monitoring status

Sometimes we need to turn on a switch port loopback monitoring capabilities, the first to take a look at the corresponding port loopback monitoring status, if you find a corresponding port loopback monitoring function is already running, it does not need to repeat the "loopback-detectionenable" string command. To view a specific Ethernet port loopback monitoring State, we can first by the previous operation, the switch to switch certain Ethernet port view state, after the corresponding view state string command under implemented "from the" displayloopback-detection open interface we can see the Specify Exchange port network loopback monitoring feature is enabled, if the result is displayed in the interface "Loopback-detectionisrunning", it shows the corresponding switching ports network loopback monitoring function has been successfully enabled. Of course, the results from the interface, we can see other monitoring parameters, such as network loopback monitoring intervals, network loopback monitoring of results; in other words, if the LAN network loops in really exists and the symptom, we can see from here what Exchange port network loop phenomenon, in which case the network administrator will be able to according to the results of such monitoring on the target Exchange port key checks, which can greatly improve network loops symptom resolution efficiency.

In future, we want to turn off the switch network loopback monitoring feature, you only need to switch back office interface to switch to a system view state and the State of the command line prompt string command "undoloopback-detection", all ports in a switch network loopback monitoring functions will be automatically closed.

Responding to symptoms of network loops

Enable the switch network loopback monitoring function, how do we use to monitor results, and quickly resolve network loops caused by network congestion symptom? actually, for different link types of switching ports, the switch will use different ways to resolve network loops symptoms.

For example, if specify the Ethernet port of the link type to Hybrid port and Trunk ports, the port future once there is network loops, switch system will automatically put the loopback monitoring results reported to the log file, in which case we will correspond to the port if loopback monitoring managed function enabled, the Exchange ports automatically and other isolating switch ports, then the corresponding port network loop phenomenon will not affect other switching ports working state.

If you specify the Ethernet port of the link type to Access ports, the switch network loopback monitoring function as soon as you discover the port there is network loop phenomenon, it will automatically prompt for the network administrator a subnet following an Exchange port exists loop failures and automatically close the Exchange ports for operation and monitoring of the results reported to the system log file.

Other configuration skills

For different switching ports, we need a different configuration to ensure that the LAN network is always efficient running if hastily for the Exchange ports enable network loopback monitoring feature, you may cause some strange LAN symptoms.

For example, if an Access type, compared to the wide area network switching ports or devices such as the hub of concern, it is best not to the Access switching ports enable network loopback monitoring function, otherwise the function once detected corresponding switching ports following network loop phenomenon, it will automatically close the Exchange ports working state, joint or lower line to this port Wan or LAN there would have been unable to surf the symptoms.

Up and down through the Trunk port connection of several switches, as the corresponding switching ports into virtual work subnet environment, then we should be careful to configure the Trunk port network loopback monitoring status, if we hastily the switching ports configured for loopback monitoring managed function, once one switch port the following network loop phenomenon, the work of the State of Trunk ports are automatically turned off, all the work of the State of the switch will be affected. At this point, we can try to enable all Trunk port loopback monitoring function of the network, but not the Trunk ports are configured not managed state. In future, if a port in the LAN network loop below the symptom, Trunk ports are not closed and that will force the managed network administrator if timely view switch network loopback monitoring status, you can quickly locate the event loop fault has specific switching ports, so you can efficiently solve network channel blockage symptoms.