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AR500, AR510, and AR530 V200R007 CLI-based Configuration Guide - Ethernet Switching

This document describes the configuration of Ethernet services, including configuring transparent bridge, MAC table, link aggregation, VLANs, STP/RSTP/MSTP, and so on.The document provides the configuration procedures and configuration examples to illustrate the service configuration methods and application scenario.
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Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
Basic Concepts of SEP

Basic Concepts of SEP

Network Architecture of SEP

As shown in Figure 13-2, Router1 through Router5constitute a ring and are dual-homed to an upper-layer a Layer 2 network. Two edge devices Router1 and Router5 are indirectly connected. This networking is called open-ring networking. This access mode will cause a loop on the entire network. To eliminate redundant links and ensure link connectivity, a mechanism used to prevent loops is required.

Figure 13-2 shows the typical networking of an open ring running SEP. The following describes the basic concepts of SEP.

Figure 13-2  Networking diagram of an open ring running SEP

  • SEP segment

    A SEP segment consists of interconnected Layer 2 switching devices configured with the same SEP segment ID and control VLAN ID. A SEP segment is the basic unit for SEP.

    A SEP segment is a ring or linear Ethernet topology. Each SEP segment has a control VLAN, edge interfaces, and common interfaces.

  • Control VLAN

    In a SEP segment, the control VLAN is used to transmit only SEP packets.

    Each SEP segment must have a control VLAN. After an interface is added to a SEP segment that has a control VLAN, the interface is automatically added to the control VLAN.

    Different SEP segments can use the same control VLAN.

    Different from a control VLAN, a data VLAN is used to transmit data packets.

  • Node

    Each Layer 2 switching device in a SEP segment is a node. Each node can have at most two interfaces added to the same SEP segment.

  • Interface role

    As defined in SEP, there are two interface roles: common interfaces and edge interfaces.

    As shown in Table 13-1, edge interfaces are further classified into primary edge interfaces, secondary edge interfaces, no-neighbor primary edge interfaces, and no-neighbor secondary edge interfaces.

    NOTE:

    Normally, edge interfaces and no-neighbor edge interfaces belong to different SEP segments.

    Table 13-1  Interface roles

    Interface Role

    Sub-role

    Description

    Edge interface

    Primary edge interface

    A SEP segment has only one primary edge interface, which is determined by the configuration and election.

    The primary edge interface initiates blocked interface preemption, terminates packets, and sends topology change notification messages to other networks.

    Secondary edge interface

    A SEP segment has only one secondary edge interface, which is determined by the configuration and election.

    The secondary edge interface terminates packets and sends topology change notification messages to other networks.

    No-neighbor primary edge interface

    An interface at the edge of a SEP segment is a no-neighbor edge interface, which is determined by the configuration and election.

    The no-neighbor primary edge interface terminates packets and sends topology change notification messages to other networks.

    No-neighbor primary edge interfaces are used to interconnect Huawei devices and non-Huawei devices or interconnect Huawei devices and devices that do not support SEP.

    No-neighbor secondary edge interface

    A SEP segment has only one no-neighbor secondary edge interface, which is determined by the configuration and election.

    The no-neighbor secondary edge interface terminates packets and sends topology change notification messages to other networks.

    No-neighbor secondary edge interfaces are used to interconnect Huawei devices and non-Huawei devices or interconnect Huawei devices and devices that do not support SEP.

    Common interface

    -

    In a SEP segment, all interfaces except edge interfaces are common interfaces.

    A common interface monitors the status of the directly-connected SEP link. When the link status changes, the interface sends a topology change notification message to notify its neighbors. Then the topology change notification message is flooded on the link until it finally reaches the primary edge interface. The primary edge interface determines how to process the link change.

  • Blocked interface

    In a SEP segment, some interfaces are blocked to prevent loops.

    Any interface in a SEP segment may be blocked if no interface is specified for blocking. A complete SEP segment has only one blocked interface.

  • Status of a SEP interface

    In a SEP segment, a SEP interface has two working states: Forwarding and Discarding, as shown in Table 13-2.

    Table 13-2  Interface status

    Interface Status

    Description

    Forwarding

    The interface can forward user traffic, receive and send SEP packets.

    Discarding

    The interface can receive and send SEP packets but cannot forward user traffic.

    An interface may be in Forwarding or Discarding state regardless of its role.

SEP Packet

Table 13-3 shows the types of SEP packets.

Table 13-3  Types of SEP packets

Packet Type

Packet Subtype

Description

Hello packet

-

After an interface is added to a SEP segment, neighbor negotiations start. The interface and its neighbor exchange Hello packets to establish a neighbor relationship. After neighbor negotiations succeed, the two interfaces continue to exchange Hello packets to detect their neighbor status.

LSA

LSA request packet

After an interface has SEP enabled, the interface periodically sends LSAs to its neighbor. After the state machine of the neighbor goes Up, the two interfaces update their LSA databases, that is, all topology information.

LSA ACK packet

TC packet

-

When the topology of a SEP segment changes, the device where the SEP segment and the upper-layer network are intersected sends a Topology Change (TC) packet to notify the upper-layer network. Then all nodes on the upper-layer network need to update their MAC address tables and ARP tables.

GR packet

-

When a device is performing an active/standby switchover, it sends a SEP Graceful Restart (GR) packet to instruct other nodes to prolong the aging time of the LSAs received from the device. After the active/standby switchover is complete, the device needs to send another GR packet to instruct other nodes to restore the aging time of the LSAs received from the device to the previous value.

Primary edge interface election packet

-

After an interface has SEP enabled, it considers itself the primary edge interface if it is qualified for primary edge interface selection. The interface then periodically sends primary edge interface election packets without waiting for the success of neighbor negotiations. A primary edge interface election packet contains the interface role (primary edge interface, secondary edge interface, or common interface), bridge MAC address of the interface, interface ID, and integrity of the topology database.

Preemption packet

Preemption request packet

A preemption packet is used to block a specified interface.

Preemption packets are sent by the elected primary edge interface or brother interface of a no-neighbor primary edge interface.

Preemption ACK packet

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Updated: 2019-05-25

Document ID: EDOC1000097279

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