H3C Technologies H3C S7500E Series Switches - Manual (Page 112)

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loops. The problem with STP, however, is that STP convergence time is long, which makes it not
suitable for users who have high demand on convergence speed. RRPP can meet users’ demand on
convergence speed, but it involves complicated networking and configurations and therefore is mainly
used in ring-shaped networks.
For more information about STP and RRPP, see MSTP Configuration in the Layer 2 - LAN Switching
Configuration Guide and RRPP Configuration in the High Availability Configuration Guide.
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:
z Dedicated to dual uplink networks
z Subsecond convergence
z 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 8-1 , GE2/0/1 and GE2/0/2 of Device C and GE2/0/1 and GE2/0/2 of Device D
each form a smart link group, with GE2/0/1 being active and GE2/0/2 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 8-1 , you can configure GE2/0/1 of Device C and that of Device D as master ports, and
GE2/0/2 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.