H3C Technologies H3C S7500E Series Switches - Manual (Page 114)

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Role preemption mechanism
As shown in Figure 8-1 , the link on GE2/0/1 of Device C is the master link, and the link on GE2/0/2 of
Device C is the slave link. Once the master link fails, GE2/0/1 is automatically blocked and placed in
the standby state, while GE2/0/2 takes over to forward traffic. If the smart link group is configured with
role preemption, GE2/0/1 takes over to forward traffic as soon as its link recovers, while GE2/0/2 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, thus implementing 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.
You can configure protected VLANs for a smart link group by referencing MSTIs.
Smart Link Collaboration Mechanisms
Collaboration between Smart Link and Monitor Link
Smart Link cannot sense by itself when faults occur on the uplink of the upstream devices, or when
faults are cleared. To monitor the uplink status of the upstream devices, you can configure the Monitor
Link function to monitor the uplink ports of the upstream devices. Monitor Link adapts the up/down
state of downlink ports to the up/down state of uplink ports, thus triggering Smart Link to perform link
switchover on the downstream device.
For more information about Monitor Link, see Monitor Link Configuration in the High Availability
Configuration Guide.
Collaboration between Smart Link and CC of CFD
Smart Link cannot sense by itself when faults (for example, unidirectional link, misconnected fibers,
and packet loss) occur on the intermediate devices or network paths, or when faults are cleared. To
check the link status, Smart Link ports need to use link detection protocols. When a fault is detected or
cleared, the link detection protocols inform Smart Link to switch over the links.
With the collaboration between Smart Link and the Continuity Check (CC) function of Connectivity
Fault Detection (CFD) configured, CFD notifies the ports of fault detection events on the basis of
detection VLANs and detection ports. A port responds to a continuity check event only when the
control VLAN of the smart link group to which it belongs matches the detection VLAN.
For more information about the CC function of CFD, see CFD Configuration in the High Availability
Configuration Guide.