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Problem Description.
Networking situation:
SE800 -- OSN2500 -- 2500+ -- 2016 Ethernet switch - - PC
Configure EVPL service on the transport
SE800 adopts the QinQ technology, which in essence encapsulates Layer 2 labels on the service VLANs; and Huawei OSN 3500- N2EGS2, which supports MPLS service. 2500+ devices are configured with EFT0 pure pass-through network boards.
Failure phenomenon: PC dial-up error code: 721 (verify the user name and password, and then this code appears)
SE800 -- OSN2500 -- 2500+ -- 2016 Ethernet switch - - PC
Configure EVPL service on the transport
SE800 adopts the QinQ technology, which in essence encapsulates Layer 2 labels on the service VLANs; and Huawei OSN 3500- N2EGS2, which supports MPLS service. 2500+ devices are configured with EFT0 pure pass-through network boards.
Failure phenomenon: PC dial-up error code: 721 (verify the user name and password, and then this code appears)
Alert messageNone
Processing1. Self-loop excludes SE800, Ethernet switch problem. 2.
2、Suspect that there is a problem with EVPL service configuration, recheck and confirm that the fault is still there.
3、Query the rmon count of transmission equipment, confirm that the transmission equipment have send and receive counts, proving that it is not the transmission equipment that loses the packets.
4, on-site packet capture test. It is found that the packet sent by SE800 will be stripped of the 4-byte outer label after being processed by OSN3500 's EGS2, and then when it is transmitted to the downstream switch from the 2500+ EFT board, the length of the message is only 60 bytes. After on-site testing and consulting with DigitalComm 800 to confirm, the 2016 switch used on-site cannot handle messages smaller than 64 bytes (most switches cannot handle packets smaller than 64 bytes). All 60-byte packets sent to the switch by the transmission device are discarded by the switch. As a result, the PC never receives the response message of SE800, which makes the PC dialing unsuccessful.
5. After using EMS4 single board to replace EGS2 single board on OSN3500, the service is normal.
2、Suspect that there is a problem with EVPL service configuration, recheck and confirm that the fault is still there.
3、Query the rmon count of transmission equipment, confirm that the transmission equipment have send and receive counts, proving that it is not the transmission equipment that loses the packets.
4, on-site packet capture test. It is found that the packet sent by SE800 will be stripped of the 4-byte outer label after being processed by OSN3500 's EGS2, and then when it is transmitted to the downstream switch from the 2500+ EFT board, the length of the message is only 60 bytes. After on-site testing and consulting with DigitalComm 800 to confirm, the 2016 switch used on-site cannot handle messages smaller than 64 bytes (most switches cannot handle packets smaller than 64 bytes). All 60-byte packets sent to the switch by the transmission device are discarded by the switch. As a result, the PC never receives the response message of SE800, which makes the PC dialing unsuccessful.
5. After using EMS4 single board to replace EGS2 single board on OSN3500, the service is normal.
Root cause1. Problems with SE800 or Ethernet switch
2. Problems with EVPL service configuration
3. Packet loss of transmission equipment
4. Mismatched boards
2. Problems with EVPL service configuration
3. Packet loss of transmission equipment
4. Mismatched boards
Recommendations and SummarySuggestion: Add OSN2500 SSN2EGS2 single-board short packet mending function
Summary: If the Ethernet service requested by the customer requires the support of the QinQ function, pay attention to the board configuration to avoid this kind of problem.
Summary: If the Ethernet service requested by the customer requires the support of the QinQ function, pay attention to the board configuration to avoid this kind of problem.
END
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