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How to Handle the Transparent Transmission of (R)STP Protocol Frames by the Ethernet Board EFGS EMS4

Publication Date:  2012-07-25 Views:  107 Downloads:  0

Issue Description

Ethernet boards are often involved in the networking with datacom equipment (such as the layer 2 switch). For service redundancy protection, the spanning tree protocol (STP/RSTP) often needs to be enabled in the datacom equipment in the networking. Based on the requirements on normal interconnection, if an Ethernet board is configured with the EPLAN service, the STP must also be enabled in the Ethernet board of the SDH. However, the commonly used Ethernet board EFGS does not have an MAC address. As a result, the EFGS is very complex in configuration and is subject to many restrictions. In this case, if the STP or RSTP is not enabled in the Ethernet board, can the (R)STP of the Ethernet switch work normally? 

Alarm Information


Handling Process

When the RSTP is disabled, the VB of the EFGS series Ethernet board can transparently transmit BPDUs normally. In the case of the R8C01 version, the EMS4 does not support the transparent transmission of BPDUs in the VB; but in the case of the R8C02 version, the EMS4 can broadcast transparent transmission, though the broadcast is subject to certain restrictions (150 packets/second).
When the EGS2 is configured to the EPL, the (R)STP BPDUs are handled as common Ethernet frames. Hence, if the port is of the Tag attribute, the BPDUs are discarded. To transparently transmit BPDUs in the current network, the Tag Aware attribute of the port must be adjusted to ensure that the BPDUs can be transmitted to the peer end. If the EGS2 is configured to the EPLAN, the EGS2 is no longer affected by such a restriction. In this case, the board processes the BPDUs accordingly based on whether the (R)STP is enabled or disabled. That is, if the (R)STP is enabled, the board processes the BPDUs; if the (R)STP is disabled, the board broadcasts the BPDUs to all other ports in the VB. 

Root Cause

Theoretically, if the Ethernet board can transparently forward the STP BPDU, the STP of the Ethernet switch can work normally. 


As mentioned above, if the EPLAN P2P (the VLAN filter of one VB include two ports) configuration of the Ethernet can be confirmed, the RSTP of the Ethernet switch can work normally. However, if the configuration of the EPLAN is complex, random problems may occur.
Hence, the EPL configuration is the first choice for the Ethernet networking. When the EPLAN is configured, it is suggested that the spanning tree be disabled in the entire network and the SDH protection be used as a substitute. In the case of special interrupts, the routing can be adjusted by changing the configuration of the Ethernet board.