CX11x, CX31x, CX710 (Earlier Than V6.03), and CX91x Series Switch Modules V100R001C10 Configuration Guide 12

The slave interface is blocked when the Smart Link group is enabled. If the active link becomes faulty, Smart Link unblocks the slave interface and switches traffic to the standby link.

If a Smart Link switchover is performed because of temporary link disconnection, packet forwarding and system performance are affected. To address this problem, you can set the delay in reporting a port-Up or port-Down event. When the member interfaces of a Smart Link group alternate between Up and Down, the Smart Link group waits until the delay expires, and then triggers a switchover.

An interface cannot be added to a Smart Link group in the following situations:

• The interface has been enabled with STP.
• The interface has been added to an Eth-Trunk.
  NOTE:

  Physical ports that have been added to an Eth-Trunk cannot be added to a Smart Link. Eth-Trunks are logical ports and can be added to a Smart Link.

• The interface has been added to a Monitor Link group.
• The interface has been added to another Smart Link group.

When a switchover occurs between active and standby links of a Smart Link group, existing forwarding entries no longer apply to the new topology. All the MAC address entries and ARP entries on the network need to be updated. Therefore, the Smart Link group needs to send Flush packets to notify other devices so that the other devices can update their MAC address entries and ARP entries. Because manufacturers define the format of Flush packets differently, the Flush packets described here are used for the intercommunication between Huawei devices only and the remote device must be configured to receive Flush packets.

An interface can receive Flush packets only when the control VLAN ID is configured on the interface and the interface is added to the control VLAN.

You do not need to configure all interfaces on the device to receive Flush packets from the specified control VLAN. This function needs to be configured only on interfaces on the active and standby links connecting the Smart Link device to the destination device.

As shown in Figure 11-83, SwitchA is configured with Smart Link. This function needs to be configured on Interface3 and Interface4 of SwitchB, Interface5 and Interface6 of SwitchC, and Interface7 and Interface8 of SwitchD.

Figure 11-83 Configuring interfaces to receive Flush packets

NOTE:

If interfaces are not configured to send and receive Flush packets, a Smart Link group uses the aging mechanism to update MAC address entries and ARP entries, causing slow convergence. It is recommended that the device is configured to send and receive Flush packets when a Smart Link group is configured, ensuring fast convergence.

When the active link in a Smart Link group fails, the traffic is automatically switched to the standby link. After the fault is rectified, the original active link remains blocked to ensure stable traffic transmission. To enable the original active link to transmit traffic, use either of the following methods:

• Enable revertive switching of a Smart Link group. Services are switched to the original active link when the WTR time is reached.
• Run the smart-link manual switch command to perform link switching forcibly.

NOTE:

Services can be switched between links only when both member interfaces in a Smart Link group are in Up state.

Configure revertive switching before enabling Smart Link. If Smart Link is already enabled, revertive switching can be configured only after Smart Link is disabled.

After a Smart Link group is enabled, the slave interface in the group is blocked. After the Smart Link group is disabled, the blocked standby interface is restored.