H3C S5500-SI Series, Operation Manual

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For more information about STP and RRPP, refer to MSTP Configuration in the Access Volume and
RRPP Configuration in the High Availability Volum .
Smart Link is a feature developed to address the slow convergence issue with STP. It provides link
redundancy as well as fast convergence in a dual uplink network, allowing the backup link to take over
quickly when the primary link fails. To sum up, Smart Link features the following:
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Dedicated to dual uplink networks
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Subsecond convergence
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Easy to configure
Terminology
Smart link group
A smart link group consists of only two member ports: the master and the slave. At a time, only one port
is active for forwarding, and the other port is blocked, that is, in the standby state. When link failure
occurs on the active port due to port shutdown or presence of unidirectional link for example, the
standby port becomes active to take over while the original active port transits to the blocked state.
As shown in Figure 1-1 , GE1/0/1 and GE1/0/2 of Device C and GE1/0/1 and GE1/0/2 of Device D each
form a smart link group, with GE1/0/1 being active and GE1/0/2 being standby.
Master/slave port
Master port and slave port are two port roles in a smart link group. When both ports in a smart link group
are up, the master port preferentially transits to the forwarding state, while the slave port stays in the
standby state. Once the master port fails, the slave port takes over to forward traffic.
As shown in Figure 1-1 , you can configure GE1/0/1 of Device C and that of Device D as master ports,
and GE1/0/2 of Device C and that of Device D slave ports.
Master/slave link
The link that connects the master port in a smart link group is the master link; the link that connects the
slave port is the slave link.
Protected VLAN
A smart link group controls the forwarding state of some data VLANs, which are referred to as protected
VLANs. Different smart link groups on a port control different protected VLANs. The state of the port in a
protected VLAN is determined by the state of the port in the smart link group.
Transmit control VLAN
The transmit control VLAN is used for transmitting flush messages. When link switchover occurs, the
devices (such as Device C and Device D in Figure 1-1 ) broadcast flush messages within the transmit
control VLAN.