【正文】 perform this task.? When applicable, review the Transmit (Xmit) Clock Source on the Show Physical Port Attributes dialog box and verify that it is not set to LoopTimed. The foreground diagnostic tests also require the physical port to provide clocking (set to Internal).? Note – It is remended that you run foreground diagnostics on a physical port only if it appears red on the Switch Back Panel dialog box.At a minimum, each physical port type supports basic internal and external loopback tests. Additional types of loopbacks specific to the individual media type are also available for each of the physical ports.? Nearend line loopback: Loops the receiver to the transmitter to loop the ining signal back to the farend. ? Farend loopback: Sends a code to request the far end to set itself into loopback mode. ? Payload loopback: Similar to a nearend line loopback, the loopback is made after the physical port framer device such that the signal from the outside traverses the framer device and is then looped back.? BERT: Bit Error Rate Testing (BERT) generates and monitors BERT patterns and measures the quality of data transmission.Based on the results of the diagnostic tests and/or loopback tests, you may take any number of actions, such as:? Change the physical port configuration.? Work with the carrier or customer. Keep in mind that the switch may not be the source of the problem. Carrier equipment or CPE may be causing the problem.? Replace faulty hardware.從網(wǎng)管查看和診斷端口的狀態(tài)統(tǒng)計:Physical Port Traps :從Trap告警記錄可以知道已經(jīng)發(fā)生過的端口故障.A mon physical port trap that indicates a problem is as follows:PPort switch name, slot number, port number is state with alarm typePossible state values for the physical port are Up,Down, or Testing.Possible values for the alarm type are Red, Yellow, Blue,Carrier loss, Loopback, BER Threshold, Idle, Admin DownFiber optic cable problems may be the source of the problem. Some typical problems include:? Cable break.? Improperly configured fiber optic connections. Upon installation, it is fairly mon for the transmit and receive fibers to be switched.? Dirty optical equipment.? Damaged connectors and cables.? High endtoend signal the loss is too high, the signal will be low at the receiver, causing a poor signaltonoise condition in the receiver. If the loss is too low, the power level at the receiver will be too high, causing receiver saturation. Both these conditions cause high biterror rates in digital systems or poor analog signal performance.? A failed LED or laser transmitter. 邏輯端口(Lport)故障診斷You can Identifying Logical Port Problems through: ? Traps ? Customer plaints? The trap is in the format: LPort port name at switch switch name is link protocol status Switch switch name interface down (SNMP linkDown trap) on LPort LPort name? If you notice a physical port problem at the same time that you notice a problem with a logical port associated with that physical port, then the problem lies with the physical port.檢查Lport的狀態(tài) :此為幀中繼Lport, 有LMI狀態(tài), ATM Lport沒有協(xié)議狀態(tài).Check 幀中繼LMI status and troubleshooting :When LMI Operator Status is Down, the operational status of any PVCs associated with the logical port is Inactive.LMI Operator Status could be Down for any of the following reasons:? CPE equipment, such as a router, may have been powered down.? A physical layer problem may exist. In this case, look for a trap that indicates a change in physical port status or check physical port summary statistics errors.? A Frame Relay configuration error may exist. Examples of configuration problems include a misconfigured DCE poll timer or a misconfigured logical port type.? Hardware failures may have occurred, as indicated by traps and background diagnostics.Under normal conditions:? For UNI DCE logical ports, the sum of the DCE Status Frames Transmitted and the DCE Full Status Frames Transmitted should be equal to the DCE Status Enquiry Frames Received.? For UNI DTE logical ports, the sum of the DTE Status Frames Received and the DTE Full Status Frames Received should be equal to the DTE Status Enquiry Frames Transmitted.If these statistics do not add up, a problem exists with the exchange of status enquiry and status response frames between DTE and DCE.If you notice DTE or DCE errors (such as DTE/DCE Error Frames Received or DTE/DCE Status Enquiry Frames Error Count), a link management configuration problem may exist.The problem may be that the DCE Poll Verify Timer is set to a value less than the DTE Poll Interval. This is a typical configuration error — the DCE Poll Verify Timer should be higher than the DTE Poll Interval.Some mon configuration errors may happen with logical port as follows :? Frame Relay encapsulation : Cisco router : encapsulation framerelay ietf (use FRC1490/2427 encapsulation)? LMI protocol mismatch between switch logical port and CPE (such as router)You can isolate logical port problems in two ways:? Run diagnostics and loopbacks Once you have verified that a problem exists, you can isolate the problem with internal and external diagnostics and loopbacks. These diagnostics and loopbacks are similar to the diagnostics and loopbacks you can use to test physical ports.? Change logical ports from UNI to NNIBy changing a UNI logical port to an NNI logical port, you configure the logical port to act as both DTE and DCE. The logical port can then generate a DCE status enquiry and respond to it as well.Once you change the logical port, you must place a loopback connector at either: ? The lo