H3C S5820X SERIES High Availability Configuration Manual

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H3C S5820X SERIES High Availability Configuration Manual Manual pdf 106 page image

94The problem with STP, however, is that STP convergence time is long, which makes it not suitable for userswho have high demand on convergence speed. RRPP can meet users’ demand on convergence speed,but it involves complicated networking and configurations and is mainly used in ring-shaped networks.NOTE:For more information about STP and RRPP, see theLayer 2—LAN Switching Configuration Guide and thechapter “RRPP configuration.”Smart Link is a feature developed to address the slow convergence issue with STP. It provides linkredundancy as well as fast convergence in a dual uplink network, allowing the backup link to take overquickly when the primary link fails. To sum up, Smart Link has the following features:• Dedicated to dual uplink networks• Subsecond convergence• Easy to configureTerminologySmart link groupA smart link group consists of only two member ports: the master port and the slave port. Only one portat a time is active for forwarding; the other port is blocked and in the standby state. When link failureoccurs on the active port due to port shutdown or the presence of a unidirectional link, for example, thestandby port becomes active, taking over and the original active port transitions to the blocked state.As shown in Figure 24, Port1 and Port2 of Device C and Port1 and Port2 of Device D each form a smartlink group, with Port1 being active and Port2 being standby.Master port/slave portMaster port and slave port are two port roles in a smart link group. When both ports in a smart link groupare up, the master port preferentially transitions to the forwarding state, and the slave port stays in thestandby state. Once the master port fails, the slave port takes over to forward traffic. As shown in Figure24, you can configure Port1 of Device C and that of Device D as master ports, and Port2 of Device C andthat of Device D as slave ports.Master link/slave linkThe link that connects the master port in a smart link group is the master link; the link that connects theslave port is the slave link.Protected VLANA smart link group controls the forwarding state of some data VLANs (protected VLANs). Different smartlink groups on a port control different protected VLANs. The state of the port in a protected VLAN isdetermined by the state of the port in the smart link group.Transmit control VLANThe transmit control VLAN is used for transmitting flush messages. When link switchover occurs, thedevices (such as Device C and Device D in Figure 24) broadcast flush messages within the transmitcontrol VLAN.Receive control VLANThe receive control VLAN is used for receiving and processing flush messages. When link switchoveroccurs, the devices (such as Device A, Device B, and Device E in Figure 24) receive and process flush