Operating Mechanism Of Smart Link - H3C S5120-EI Series Operation Manual

Master port
Master port is a port role in a smart link group. When both ports in a smart link group are up, the master
port preferentially transits to the forwarding state. Once the master port fails, the slave port takes over to
forward traffic. During this period, if the smart link group is not configured with role preemption, the
master port stays in standby state until the next link switchover even if it has recovered.
As shown in Figure
ports.
Slave port
Slave port is a port role in a smart link group. When both ports in a smart link group are up, the slave
port is placed in the standby state. When the master port fails, the slave port takes over to forward
traffic.
As shown in Figure
Flush message
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.
Transmit control VLAN
The transmit control VLAN is used for transmitting flush messages. When link switchover occurs, the
devices (such as Device C and E in
VLAN.
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, B, and D in
the receive control VLAN and refresh their MAC address forwarding entries and ARP/ND entries.
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.

Operating Mechanism of Smart Link

Link backup mechanism
As shown in Figure
Device C is the standby link. Normally, GE1/0/1 is in the forwarding state, while GE1/0/2 is in the
standby state. When the link on GE1/0/1 fails, GE1/0/2 takes over to forward traffic while GE1/0/1 is
blocked and placed in the standby state.
When a port switches to the forwarding state, the system outputs log information to notify the user of the
port state change.
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:
1-1, you can configure GE1/0/1 of Device C and GE1/0/2 of Device E as master
1-1, you can configure GE1/0/2 of Device C and GE1/0/1 of Device E as slave ports.
Figure
1-1, the link on GE1/0/1 of Device C is the active link, and the link on GE1/0/2 of
1-1) broadcast flush messages within the transmit control
Figure 1-1) receive and process flush messages in
1-2