H3C Technologies H3C S12500 Series Switches - Manual (Page 116)

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• Subsecond convergence
• 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, in other words, in 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 23 , GigabitEthernet 4/0/1 and GigabitEthernet 4/0/2 of Switch C and
GigabitEthernet 4/0/1 and GigabitEthernet 4/0/2 of Switch D each form a smart link group, with
GigabitEthernet 4/0/1 being active and GigabitEthernet 4/0/2 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
standby state. Once the master port fails, the slave port takes over to forward traffic. As shown in Figure
23 , you can configure GigabitEthernet 4/0/1 of Switch C and that of Switch D as master ports, and
GigabitEthernet 4/0/2 of Switch C and that of Switch 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.
Flush message
Flush messages are used by a smart link group to notify other switches 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.
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
switches (such as Switch C and Switch D in Figure 23 ) broadcast flush messages within the transmit
control VLAN.
Receive control VLAN
The receive control VLAN is used for receiving and processing flush messages. When link switchover
occurs, the switches (such as Switch A, Switch B, and Switch E in Figure 23 ) receive and process flush
messages in the receive control VLAN and refresh their MAC address forwarding entries and ARP/ND
entries.