E1 error packet analysis and loopback detection method

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1. Causes and solutions for error packets on the E1/SA interface
E1 interface:
- A lot of error packets are detected in CRC. The CRC-16 algorithm is used on Huawei devices by default. You can try to resolve this problem by using the CRC-32 algorithm.
- No Buffers: Input or output traffic suddenly surges. If the sudden surge of input traffic is measured, a downlink CAR can be set for the upstream device.
If the sudden surge of output traffic is measured, a CAR can be set on the egress of the Huawei device.
- The state of the E1-M interface (unframed) cannot be Up after the cable connected to it is disconnected first and then connected again. In this case, you can try to disable the AIS detection by running the undo detect-ais command in controller configuration mode.
- Alignments error packets are measured. In this case, you can run the following command to modify the clock and ensure that one of the clocks on both ends is the master clock:
fe1 clock master
SA interface:
- A lot of error packets are detected in CRC. The CRC-16 algorithm is used on Huawei devices by default. You can try to resolve this problem by using the CRC-32 algorithm.
- If the number of input error packets of the AR router surges when the AR router is in DTE mode, you can try to invert the receive clock by running the following command:
invert receive-clock
If the number of input error packets of the peer device surges, you can try to invert the transmit clock by running the following command:
invert transmit-clock
- When the AR router is in DTE mode, run the following command to adjust the bandwidth of the interface by setting the virtual baud rate based on the actual bandwidth of physical links.
virtualbaudrate baudrate (the baud rate is 64 kbit/s by default)
2. Interconnection failures between the E1 interface and devices of competitors
- Check the configuration and confirm that no error packets are detected on the interface, eliminating possibilities of error packets being caused by configurations, CRC, or cables.
- Check causes by segments.
3. GE optical interface interconnection failures
List of consulted problems
- The state of the optical interface of AR2240 or AR3260 cannot be Up after AR2240 or AR3260 is connected to an optical module.
An optical-electrical multiplex interface works as an electrical interface by default. Therefore, the interface must be manually configured as an optical interface if the AR router is connected to an optical module.
You can run the combo-port fiber command to configure the interface as an optical interface.
- Information about the optical module is not displayed after the display transceiver command is run.
Only information about optical modules authorized by Huawei is displayed after the command is run.
- Does AR2240/3260 support both 100M and 1000M optical modules and adapt its rate to different optical modules?
AR2240/3260 supports both 100M and 1000M optical modules and can adapt its rate to different optical modules.

For details, see the following URL: FAQ-E1错包分析和自环检测方�?/a>.

Other related questions:
Loopback detection usage scenario of S series switch
S series switches (except S1700) can detect self-loops on an interface, loops on the downstream network, and loops between interfaces. 1. Detect self-loops on an interface. During network deployment, Tx-Rx (fiber transmit end and fiber receive end) self-loops often occur on interfaces. For example, Tx-Rx self-loops often occur when the fiber is inserted incorrectly or the local interface is damaged by high voltage. A self-loop occurs on the interface of the Switch; as a result, packets sent by the interface are sent back to this interface. This may cause problems such as abnormal traffic forwarding and MAC address flapping. 2. A loop occurs on the downstream network or device of the Switch. As a result, packets sent by Interface1 are sent back to this interface after passing through the downstream network or device of the Switch. 3. A loop occurs on the network or between interfaces of the Switch. As a result, packets sent by Interface1 are sent back to Interface2.

Configure single-interface loopback detection on S series switch
How to configure single-interface loopback detection on S series switches (except S1700)? Among external loopback detection, only single-interface loopback detection is supported on switches. After external loopback detection is enabled on an Ethernet interface of a switch, the switch periodically checks whether external loopback occurs on each Ethernet interface. If an S series switch finds that external loopback occurs on an Ethernet interface, by default, it blocks the interface when it runs a version earlier than V200R001 or shuts down the interface when it runs V200R001 or a later version. If an E series switch finds that external loopback occurs on an Ethernet interface, by default, it shuts down the interface. 1. Application Scenario In actual networking, single-interface loopback detection is often used on a downlink interface of a newly deployed or added access switch. You are advised to set the action taken after loopback is detected to block. 2. Configuration Procedure Enable loopback detection globally. This function will then be enabled on all interfaces simultaneously. [Huawei] loopback-detect enable Modular switches running V200R001 or later support loopback detection in a maximum of eight VLANs. Fixed switches running V100R005 or later support loopback detection in a maximum of eight VLANs. E series switches support loopback detection in a maximum of eight VLANs. The following example describes how to configure loopback detection on a fixed switch: [Huawei-Ethernet0/0/1] loopback-detect packet vlan 20 21 22 23 24 25 26 27 [Huawei-Ethernet0/0/1] loopback-detect action block Among E series switches, modular switches running V200R001 and fixed switches running V100R005 or later save loopback alarm information in the trap buffer, and the alarm information can also contain information about the VLAN in which loopback is detected. Alarm information is as follows: #Jan 1 2008 06:43:54-08:00 Quidway LDT/4/Porttrap:OID1.3.6.1.4.1.2011.5.25.174.3.3 Loopback does exist on interface(5) Ethernet0/0/1 ( VLAN 20 ) , loopback detect status: 4.(1:normal; 2:block;3:shutdown; 4:trap; 5:nolearn) 3. Precautions Loopback detection will consume some system resources. After deploying or adding access switches, run the undo loopback-detect enable command to disable this function.

Does the U1900 series unified gateway support loopback test
Method of performing the loopback test for the E1 line on the U1900: - Physically connect a pair of tx and rx ports of the E1 line, and obseve the RFA indicator and LOS indicator on the U1900. If they are both off, the local loopback test is successfully.

Meanings and methods of different loopbacks on an MSTP device
Meanings and methods of different loopbacks on an MSTP device: 1. Software loopback: indicates loopbacks (except physical loopbacks) that can be set on the NMS. For a line optical board, you can open the channel diagram and set loopbacks for optical interfaces and VC-4 channels. Pay attention to the monitoring channels. Otherwise, the MSTP device may be unreachable to the NMS. Software loopbacks cannot be set for VC-12 channels. For a 2M tributary board, the software loopback can be set for each 2M interface. 2. Inloop and outloop: These two types of loops are different in the direction. An inloop indicates a loop from an interface to the inside of a device. An outloop indicates a loop from an interface to the outside of a device.

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