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Configuration Guide - Ethernet Switching

S1720, S2700, S5700, and S6720 V200R012(C00 and C20)

This document describes the configuration of Ethernet services, including configuring MAC address table, link aggregation, VLANs, VLAN aggregation, MUX VLAN, VLAN termination, Voice VLAN, VLAN mapping, QinQ, GVRP, VCMP, STP/RSTP/MSTP, VBST, SEP, RRPP, ERPS, LBDT, and Layer 2 protocol transparent transmission.
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Link Aggregation in Stack Scenarios

Link Aggregation in Stack Scenarios


  • Stack device

    A stack device is a logical device formed by connecting multiple devices through stack cables. In Figure 3-11, DeviceB and DeviceC are connected to form a logical device.

  • Inter-chassis Eth-Trunk

    An inter-chassis Eth-Trunk contains physical interfaces of multiple devices in a stack. When a device in the stack fails or a physical interface added to the Eth-Trunk fails, traffic can be transmitted between devices through stack cables. The inter-chassis Eth-Trunk ensures reliable transmission and implements device backup.

  • Preferential forwarding of local traffic

    In network b of Figure 3-11, traffic from DeviceB or DeviceC is only forwarded through local member interfaces when the network runs properly. In network a of Figure 3-11, traffic is forwarded across devices through stack cables.

    Figure 3-11  Inter-chassis Eth-Trunk

Inter-Chassis Eth-Trunk Supporting Preferential Forwarding of Local Traffic

Inter-chassis Eth-Trunk supporting preferential forwarding of local traffic saves bandwidth resources between devices and improves traffic forwarding efficiency. In a stack, an Eth-Trunk is configured to be the outbound interface of traffic to ensure reliable transmission. Member interfaces of the Eth-Trunk are located on different devices. If preferential forwarding of local traffic is not enabled, when the stack device forwards traffic, the Eth-Trunk may select an inter-chassis member interface based on the hash algorithm. This forwarding mode occupies bandwidth resources between devices and reduces traffic forwarding efficiency.

As shown in Figure 3-11, DeviceB and DeviceC constitute a stack, and the stack connects to DeviceA through an Eth-Trunk. After the Eth-Trunk in the stack is configured to preferentially forward local traffic, the following functions are implemented:

  • Forwarding received traffic by the local device

    When DeviceB has member interfaces of the Eth-Trunk and the member interfaces function properly, the Eth-Trunk forwarding table of DeviceB contains only local member interfaces. In this manner, the hash algorithm selects a local member interface, and traffic is only forwarded through DeviceB.

  • Forwarding received traffic by another device

    When DeviceB does not have any member interface of the Eth-Trunk or all member interfaces are faulty, the Eth-Trunk forwarding table of DeviceB contains all available member interfaces. In this manner, the hash algorithm selects a member interface on DeviceC, and traffic is forwarded through DeviceC.

  • This function is only valid for known unicast packets, and is invalid for unknown unicast packets, broadcast packets, and multicast packets.
  • Before configuring an Eth-Trunk to preferentially forward local traffic, ensure that member interfaces of the local Eth-Trunk have sufficient bandwidth to forward local traffic; otherwise, traffic may be discarded.
Updated: 2018-12-24

Document ID: EDOC1100038339

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