Smart Link Group

A Smart Link group consists of two interfaces: a master interface and a slave interface. Normally, the master interface is in active state, and the slave interface is blocked and in inactive state.

As shown in Figure 5-2, Interface1 and Interface2 on SwitchD form a Smart Link group.

Master and Slave Interfaces

In the Smart Link group shown in Figure 5-2, Interface1 is the master interface, and Interface2 is the slave interface. When the two interfaces are both Up, the master interface is active and the slave interface is inactive. If the link on the master interface fails, the slave interface becomes active and transitions to the forwarding state.

Flush Packet

When a link switchover occurs in a Smart Link group, existing forwarding entries no longer apply to the new topology. Therefore, all the MAC address entries and ARP entries on the network need to be updated. In this situation, the Smart Link group sends Flush packets to notify other devices of updates in MAC address entries and ARP entries. In Figure 5-2, when a link switchover occurs, SwitchD sends a multicast Flush packet to notify SwitchA, SwitchB, and SwitchC that they need to update their MAC address entries and ARP entries.

Control VLAN

• Control VLAN for sending Flush packets

  A Smart Link group broadcasts Flush packets in this VLAN. In Figure 5-2, if SwitchD is enabled to send Flush packets, it broadcasts Flush packets in the control VLAN when a link switchover occurs in the Smart Link group.

• Control VLAN for receiving Flush packets

  The upstream devices use the control VLAN to accept and process Flush packets. In Figure 5-2, upstream devices SwitchA, SwitchB, and SwitchC are able to identify Flush packets and are enabled to process Flush packets. When a link switchover occurs on SwitchD, the upstream devices process the received Flush packets and update their MAC address entries and ARP entries.

Load Balancing

Links in a Smart Link group can forward different data flows when they are working normally. You can configure multiple load balancing instances and bind VLANs to the instances. In load balancing mode, both the interfaces are active. The slave interface forwards traffic from the VLANs associated with the load balancing instances and the master interface forwards traffic from other VLANs. If a link fails, the Smart Link group automatically switches all traffic to the other link.

Smart Link Instance

The backup link in a Smart Link group can be bound to multiple instances to implement load balancing. Smart Link uses the instances defined in the Multiple Spanning Tree Protocol (MSTP). Each instance can be bound to multiple VLANs, and multiple instances can be bound to different VLANs.