How Smart Link Works - H3C S5820X SERIES High Availability Configuration Manual

messages in the receive control VLAN and refresh their MAC address forwarding entries and ARP/ND
entries.
Flush message
Flush messages are used by a smart link group to notify other devices to refresh their MAC address
forwarding entries and ARP/ND entries when link switchover occurs in the smart link group. Flush
messages are common multicast data packets, and will be dropped by a blocked receiving port.

How Smart Link works

Link backup mechanism
As shown in
C is the slave link. Typically, Port1 is in the forwarding state, and Port2 is in the standby state. When the
master link fails, Port2 takes over to forward traffic and Port1 is blocked and placed in the standby state.
NOTE:
When a port switches to the forwarding state, the system outputs log information to notify the user of the
port state change.
Topology change mechanism
As link switchover can outdate the MAC address forwarding entries and ARP/ND entries on all network
devices, you need a forwarding entry update mechanism to ensure proper transmission. The following
update mechanisms are provided:
Uplink traffic-triggered MAC address learning, where update is triggered by uplink traffic. This
•
mechanism is applicable to environments with network devices that do not support Smart Link,
including devices of other vendors.
• Flush update where a Smart Link-enabled device updates its information by transmitting flush
messages over the backup link to its upstream devices. This mechanism requires the upstream
device to be capable of recognizing Smart Link flush messages to update its MAC address
forwarding entries and ARP/ND entries.
Role preemption mechanism
As shown in
C is the slave link. Once the master link fails, Port1 is automatically blocked and placed in the standby
state, and Port2 takes over to forward traffic.
When the master link recovers:
If the smart link group is not configured with role preemption, Port1 stays blocked, and no link
•
switchover occurs, ensuring traffic stability. Port1 does not transition to the forwarding state until the
next link switchover occurs.
If the smart link group is configured with role preemption, Port1 takes over to forward traffic as soon
•
as its link recovers, and Port2 is automatically blocked and placed in the standby state.
Load sharing mechanism
A ring network may carry traffic of multiple VLANs. Smart Link can forward traffic of different VLANs in
different smart link groups, to implement load sharing.
To implement load sharing, you can assign a port to multiple smart link groups (each configured with
different protected VLANs), making sure that the state of the port is different in these smart link groups.
In this way, traffic of different VLANs can be forwarded along different paths.
24, the link on Port1 of Device C is the master link, and the link on Port2 of Device
Figure
24, the link on Port1 of Device C is the master link, and the link on Port2 of Device
Figure
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