Inter-Device Link Aggregation

Stacking

Interfaces on member switches in a stack can be bundled into an Eth-Trunk.

This inter-device link aggregation mode is applied to scenarios where the stack is connected to other devices, and protects the link between upstream and downstream devices. The Eth-Trunk can still work even if a member switch fails or one link of the Eth-Trunk fails, ensuring reliable transmission of data traffic. This prevents single-point failures of a member device in a stack and greatly improves the network-wide reliability.

For details, see Stack Configuration in the CloudEngine 12800 and 12800E Series Switches Configuration Guide - Virtualization Configuration Guide.

Figure 3-11 Physical and logical topologies of inter-device link aggregation in a stack

M-LAG

M-LAG allows two access switches in the same state to perform link aggregation negotiation with the access device. In Figure 3-12, the access device communicates with the M-LAG through link aggregation, achieving device-level reliability instead of only card-level reliability. The M-LAG is a dual-active system that is composed of two access switches.

M-LAG is a horizontal virtualization technology that virtualizes two M-LAG devices into one logical device, that is, a unified Layer 2 logical node. In practice, M-LAG provides loop-free networking between aggregation and access layers and replaces STP. Compared with STP, M-LAG provides clear logical topology and better link use efficiency.

M-LAG master and backup devices forward data simultaneously and their forwarding behaviors are the same. The forwarding behaviors of M-LAG master and backup device roles are different only in scenarios where faults occur.

For details, see M-LAG Configuration in the CloudEngine 12800 and 12800E Series Switches Configuration Guide - Ethernet Switching Configuration Guide.

Figure 3-12 Physical and logical topologies of inter-device link aggregation in an M-LAG system

M-LAG Lite

Figure 3 shows the inter-device link aggregation on the M-LAG Lite networking. Compared with inter-device link aggregation in a stack or M-LAG system, inter-device link aggregation in an M-LAG Lite system removes the heartbeat cable (CSS link or peer-link) required for establishing a stack/M-LAG between devices. Inter-device link aggregation in an M-LAG Lite system simplifies deployment, saves costs, and ensures that services are not interrupted during the upgrade.

In Figure 3, the same Eth-Trunk ID, LACP system ID, LACP system priority, and different numbers of Eth-Trunk member interfaces are configured on DeviceB and DeviceC. (On one member device, the lacp port-id-extension enable command is run in views of all the member interfaces to increase the number of each member interface by 32768.) In this way, the inter-device Eth-Trunk interface negotiation can be successful. The two devices evenly load balance data. When one device fails, traffic can be forwarded through the other device, implementing device-level reliability.

DeviceB and DeviceC must be Layer 3 gateways and cannot be Layer 2 transparent transmission devices. If an upstream device functions as the gateway, the ARP and ND entries of the server or switch learned by the gateway have two egresses, causing MAC address flapping. Therefore, the devices to which the server or switch connects in M-LAG Lite mode must be Layer 3 gateways.

For details about M-LAG Lite, see "Example for Configuring M-LAG Lite" in Configuration Examples for Comprehensive Scenarios in the CloudEngine 12800 and 12800E Series Switches Configuration Guide - Typical Configuration Examples. For details about IPv6 M-LAG Lite, see "Example for Configuring IPv6 M-LAG Lite" in Configuration Examples for Comprehensive Scenarios in the CloudEngine 12800 and 12800E Series Switches Configuration Guide - Typical Configuration Examples.

Figure 3-13 Inter-device link aggregation in M-LAG Lite networking