3com S7906E 安装指导

 

1-4 

Receive control VLAN 

The receive control VLAN is used for receiving and processing flush messages. When link switchover 

occurs, the devices (such as Device A, Device B, and Device E in 

) receive and process flush 

messages in the receive control VLAN and refresh their MAC address forwarding entries and ARP/ND 

entries.  

Flush messages are used by a smart link group to notify other devices to refresh their MAC address 

forwarding entries and ARP/ND entries when link switchover occurs in the smart link group. Flush 

messages are common multicast data packets, and will be dropped by a blocked receiving port.  

As shown in 

, 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. Normally, GE2/0/1 is in the forwarding state, while GE2/0/2 is in the standby 

state. When the master link fails, GE2/0/2 takes over to forward traffic while GE2/0/1 is blocked and 

placed in the standby state.  

 

z 

When a port switches to the forwarding state, the system outputs log information to notify the user 

of the port state change. 

z 

To keep traffic forwarding stable, the master port that has been blocked due to link failure does not 

take over immediately upon its recovery. Instead, link switchover will occur at next link switchover.  

 

As link switchover can outdate the MAC address forwarding entries and ARP/ND entries on all devices, 

you need a forwarding entry update mechanism to ensure proper transmission. By far, the following two 

update mechanisms are provided: 

z 

Uplink traffic-triggered MAC address learning, where update is triggered by uplink traffic. This 

mechanism is applicable to environments with devices not supporting smart link, including devices 

of other vendors’.  

z 

Flush update where a Smart Link-enabled device updates its information by transmitting flush 

messages over the backup link to its upstream devices. This mechanism requires the upstream 

devices to be capable of recognizing smart link flush messages to update its MAC address 

forwarding entries and ARP/ND entries.  

As shown in 

, 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. During this period, if the smart link group is