H3C S5120-EI Series Configuration Manual

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H3C S5120-EI Series Configuration Manual Manual pdf 107 page image

98How Smart Link worksLink backup mechanismAs shown in Figure 22, the link on Port1 of Device C is the master link, and the link on Port2 of DeviceC is the slave link. Typically, Port1 is in forwarding state, and Port2 is in standby state. When the masterlink fails, Port2 takes over to forward traffic and Port1 is blocked and placed in standby state.NOTE:When a port switches to the forwarding state, the system outputs log information to notify the user of theport state change.Topology change mechanismBecause link switchover can outdate the MAC address forwarding entries and ARP/ND entries on alldevices, you need a forwarding entry update mechanism to ensure proper transmission. By far, thefollowing two update mechanisms are provided:• Uplink traffic-triggered MAC address learning, where update is triggered by uplink traffic. Thismechanism is applicable to environments with devices not supporting Smart Link, including devicesof other vendors’.• Flush update where a Smart Link-enabled device updates its information by transmitting flushmessages over the backup link to its upstream devices. This mechanism requires the upstreamdevices to be capable of recognizing Smart Link flush messages to update its MAC addressforwarding entries and ARP/ND entries.Role preemption mechanismAs shown in Figure 22, the link on Port1 of Device C is the master link, and the link on Port2 of DeviceC is the slave link. Once the master link fails, Port1 is automatically blocked and placed in standby state,and Port2 takes over to forward traffic. When the master link recovers, one of the following occurs:• If the smart link group is not configured with role preemption, to keep traffic forwarding stable,Port1 that has been blocked due to link failure does not immediately take over to forward traffic.Rather, it stays blocked until the next link switchover.• If the smart link group is configured with role preemption, Port1 takes over to forward traffic as soonas its link recovers, and Port2 is automatically blocked and placed in standby state.Load sharing mechanismA ring network may carry traffic of multiple VLANs. Smart Link can forward traffic of different VLANs indifferent smart link groups, implementing load sharing.To implement load sharing, you can assign a port to multiple smart link groups (each configured withdifferent 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 Multiple Spanning TreeInstances (MSTIs).Smart Link collaboration mechanismsCollaboration between Smart Link and Monitor LinkSmart Link cannot sense by itself when faults occur on the uplink of the upstream devices, or when faultsare cleared. To monitor the uplink status of the upstream devices, you can configure the Monitor Link