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Ethernet Service Is Unavailable Because the N2EGS2 Board Does Not Support the Short Packet Supplement Function

Publication Date:  2019-07-03 Views:  106 Downloads:  0

Issue Description

SE800――OSN3500――2500+――2016 Ethernet switch ――PC
The transmission is configured with the EVPL service
The SE800 uses the QinQ technology, that is, encapsulates layer 2 labels in the service VLAN. Huawei OptiX OSN3500-N2EGS2 supports the MPLS service. The OptiX OSN 2500+ is configured with the pure EFT0 transparent transmission board.
Symptom: The error code for dialup access of the PC is 721, which is displayed after the username and password is authenticated. 

Alarm Information


Handling Process

1. Rule out the fault of the Ethernet switch and the SE800 by performing a selfloop.
2. The EVPL service configuration is probably faulty. Check the EVPL service configuration and find that the configuration is correct. But the fault persists.
3. Check the RMON count at the transmission equipment. The count of the transmission equipment exists, which proves that the loss of the packets is not caused by the transmission equipment.
4, Perform a anlyze detail information test. In the test, the packets transmitted by the SE800 are processed by the EGS2 of the OptiX OSN 3500, and the external layer tags of four bytes are discarded. The packets are transparently transmitted to the downstream switch from the EFT board of the OptiX OSN 2500+, and only 60 bytes are left. The field test and the information from the toll-free phone of the data communication indicate that the field 2016 switch cannot process the packets that are smaller than 64 bytes. Most switches cannot process such packets. The 60 bytes transmitted from the transmission equipment to the switch are discarded by the switch. As a result, the PC cannot receive the response packets of the SE800, and the PC fails to dial up.
5. On the OptiX OSN 3500, replace the EMS4 board with an EGS2 board. The service recovers. 

Root Cause

1. The SE800 or the Ethernet switch is faulty.
2. The EVPL service configuration is incorrect.
3. The transmission equipment discards packets.
4. The interconnection of the boards does not match. 


Suggestion: Enable the short packet supplement function on the EGS2 board.
Summary: If the QinQ function is required in the Ethernet service, try to avoid such fault through board configuration.