08-Smart Link Configuration
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Table of Contents
Operating Mechanism of Smart Link
Smart Link Configuration Task List
Configuring a Smart Link Device
Configuring Protected VLANs for a Smart Link Group
Configuring Member Ports for a Smart Link Group
Configuring Role Preemption for a Smart Link Group
Enabling the Sending of Flush Messages
Smart Link Device Configuration Example
Configuring an Associated Device
Enabling the Receiving of Flush Messages
Associated Device Configuration Example
Displaying and Maintaining Smart Link
Smart Link Configuration Examples
Single Smart Link Group Configuration Example
Multiple Smart Link Groups Load Sharing Configuration Example
When configuring Smart Link, go to these sections for information that you are interested in:
l Configuring a Smart Link Device
l Configuring an Associated Device
l Displaying and Maintaining Smart Link
l Smart Link Configuration Examples
In most cases, Spanning Tree Protocol (STP) is used to remove network loops while delivering link redundancy in a dual uplink network. The problem with STP, however, is that STP convergence time is long, which makes it not suitable for users who have high demand on convergence speed.
For more information about STP, refer to MSTP Configuration in the Access Volume.
Smart Link is a feature developed to address the slow convergence issue with STP. It provides link redundancy as well as fast convergence in a dual uplink network, allowing the backup link to take over quickly when the primary link fails. To sum up, Smart Link features the following:
l Dedicated to dual uplink networks
l Subsecond convergence
l Easy to configure
Figure 1-1 shows a Smart Link application scenario.
Figure 1-1 Smart Link application scenario
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, that is, in the 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 1-1, GE1/0/1 and GE1/0/2 of Device C form a smart link group, with GE1/0/1 being active and GE1/0/2 being standby. GE1/0/1 and GE1/0/2 of Device E form another smart link group, with GE1/0/2 being active and GE1/0/1 being standby.
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 1-1, you can configure GE1/0/1 of Device C and GE1/0/2 of Device E as master ports.
As shown in Figure 1-1, you can configure GE1/0/2 of Device C and GE1/0/1 of Device E as slave ports.
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.
The transmit control VLAN is used for transmitting flush messages. When link switchover occurs, the devices (such as Device C and E in Figure 1-1) broadcast flush messages within the transmit 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 Figure 1-1) receive and process flush messages in the receive control VLAN and refresh their MAC address forwarding entries and ARP/ND entries.
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.
As shown in Figure 1-1, the link on GE1/0/1 of Device C is the active link, and the link on GE1/0/2 of 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:
l 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’.
l 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.
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 shown in Figure 1-1, the link on GE1/0/1 of Device C is the active link, and the link on GE1/0/2 of Device C is the standby link. Once GE1/0/1 fails, GE1/0/2 takes over to forward traffic. During this period, if the smart link group is configured with role preemption, GE1/0/1 takes over to forward traffic as soon as it recovers.
A ring network may carry traffic of multiple VLANs. Smart link can forward traffic of different VLANs in different smart link groups, thus implementing load sharing.
To implement load sharing, you can assign a port to multiple smart link groups (each configured with different 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 MSTIs.
Complete the following tasks to configure Smart Link:
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Task |
Remarks |
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Required |
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Required |
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Optional |
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Optional |
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Required |
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l A smart link device is a device that supports Smart Link and is configured with a smart link group and a transmit control VLAN for flush message transmission. Device C and Device E in Figure 1-1 are two examples of smart link devices.
l An associated device is a device that supports Smart Link, and receives flush messages sent from the specified control VLAN. Device A, Device B, and Device D in Figure 1-1 are examples of associated devices.
l Before configuring a port as a smart link group member, shut down the port to prevent loops. You can bring up the port only after completing the smart link group configuration.
l Disable STP and RRPP on the ports you want to add to the smart link group, and make sure that the ports are not member ports of any aggregation group or service loopback group.
Follow these steps to configure the protected VLANs for a smart link group:
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To do… |
Use the command… |
Remarks |
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Enter system view |
system-view |
— |
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Create a smart link group and enter smart link group view |
smart-link group group-id |
— |
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Configure protected VLANs for the smart link group |
protected-vlan reference-instance instance-id-list |
Required By default, no protected VLAN is configured for a smart link group. |
The protected-vlan command configures protected VLANs for a smart link group by referencing MSTIs. To view VLAN-to-MSTI mappings, use the display stp region-configuration command. For VLAN-to-MSTI mapping configuration, refer to MSTP Configuration in the Access Volume.
You can configure member ports for a smart link group either in smart link group view or in interface view. The configurations made in these two views have the same effect.
Follow these steps to configure member ports for a smart link group in smart link group view:
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To do… |
Use the command… |
Remarks |
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Enter system view |
system-view |
— |
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Create a smart link group and enter smart link group view |
smart-link group group-id |
— |
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Configure member ports for a smart link group |
port interface-type interface-number { master | slave } |
Required |
Follow these steps to configure member ports for a smart link group in interface view:
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To do… |
Use the command… |
Remarks |
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Enter system view |
system-view |
— |
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Enter Ethernet interface view or layer 2 aggregate interface view |
interface interface-type interface-number |
— |
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Configure member ports for a smart link group |
port smart-link group group-id { master | slave } |
Required |
Follow these steps to configure role preemption for a smart link group:
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To do… |
Use the command… |
Remarks |
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Enter system view |
system-view |
— |
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Create a smart link group and enter smart link group view |
smart-link group group-id |
— |
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Enable role preemption |
preemption mode role |
Optional Enabled by default. |
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Configure the preemption delay |
preemption delay delay-time |
Optional 1 second by default |
The preemption delay configuration takes effect only after role preemption is enabled.
Follow these steps to enable the sending of flush messages:
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To do… |
Use the command… |
Remarks |
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Enter system view |
system-view |
— |
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Create a smart link group and enter smart link group view |
smart-link group group-id |
Required |
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Enable flush update in the specified control VLAN |
flush enable [ control-vlan vlan-id ] |
Optional By default, flush update is enabled, and VLAN 1 is the control VLAN. |
l The control VLAN configured for a smart link group must be different from that configured for any other smart link group.
l Make sure that the configured control VLAN already exists, and assign the smart link group member ports to the control VLAN.
l Do not remove the control VLAN. Otherwise, flush messages cannot be sent properly.
l Create smart link group 1.
l The protected VLANs of smart link group 1 are mapped to MSTI 0 through 8.
l Configure GigabitEthernet 1/0/1 as the master port of the smart link group, and GigabitEthernet 1/0/2 as the slave port.
l Configure VLAN 20 for flush update.
l Configure the collaboration between Smart Link and the CC function of CFD on GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2.
<Sysname> system-view
[Sysname] vlan 20
[Sysname-vlan20] quit
[Sysname] interface gigabitethernet 1/0/1
[Sysname-GigabitEthernet1/0/1] undo stp enable
[Sysname-GigabitEthernet1/0/1] port link-type trunk
[Sysname-GigabitEthernet1/0/1] port trunk permit vlan 20
[Sysname-GigabitEthernet1/0/1] quit
[Sysname] interface gigabitethernet 1/0/2
[Sysname-GigabitEthernet1/0/2] undo stp enable
[Sysname-GigabitEthernet1/0/2] port link-type trunk
[Sysname-GigabitEthernet1/0/2] port trunk permit vlan 20
[Sysname-GigabitEthernet1/0/2] quit
[Sysname] smart-link group 1
[Sysname-smlk-group1] protected-vlan reference-instance 0 to 8
[Sysname-smlk-group1] port gigabitethernet1/0/1 master
[Sysname-smlk-group1] port gigabitethernet1/0/2 slave
[Sysname-smlk-group1] flush enable control-vlan 20
[Sysname-smlk-group1] quit
You do not need to enable all ports on the associated devices to receive flush messages sent from the transmit control VLAN, only those on the active and standby links between the smart link device and the destination device.
For example, as all the numbered ports on Device A, B, and D in Figure 1-1 are on the active or standby links from Devices C and E to Device A, you need to enable the ports to process flush messages received from the control VLAN configured on Device C and E.
Follow these steps to enable the receiving of flush messages:
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To do… |
Use the command… |
Remarks |
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Enter system view |
system-view |
— |
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Enter Ethernet interface view or Layer 2 aggregate interface view |
interface interface-type interface-number |
— |
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Configure the control VLANs for receiving flush messages |
smart-link flush enable [ control-vlan vlan-id-list ] |
Required By default, no control VLAN exists for receiving flush messages. |
l Configure all the control VLANs to receive flush messages.
l If no control VLAN is specified for processing flush messages, the device forwards the received flush messages without processing them.
l Make sure that the receive control VLAN is the same as the transmit control VLAN configured on the smart link device. If they are not the same, the associated device will forward the received flush messages directly without any processing.
l Do not remove the control VLANs. Otherwise, flush messages cannot be sent properly.
l Make sure that the control VLANs are existing VLANs, and assign the ports capable of receiving flush messages to the control VLANs.
Configure GigabitEthernet 1/0/1 to receive and process flush messages in VLAN 20.
<Sysname> system-view
[Sysname] vlan 20
[Sysname-vlan20] quit
[Sysname] interface gigabitethernet1/0/1
[Sysname-GigabitEthernet1/0/1] port link-type trunk
[Sysname-GigabitEthernet1/0/1] port trunk permit vlan 20
[Sysname-GigabitEthernet1/0/1] smart-link flush enable control-vlan 20
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To do... |
Use the command… |
Remarks |
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Display smart link group information |
display smart-link group { group-id | all } |
Available in any view |
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Display information about the received flush messages |
display smart-link flush |
Available in any view |
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Clear the statistics about flush messages |
reset smart-link statistics |
Available in user view |
As shown in Figure 1-2, both Device C and Device E are dually uplinked to Device A.
Configure Smart Link on the devices for uplink backup, adopting VLAN 1 (the default) for flush update.
Figure 1-2 Single smart link group configuration
1) Configuration on Device C
# Disable STP on GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2.
<DeviceC> system-view
[DeviceC] interface gigabitethernet 1/0/1
[DeviceC-GigabitEthernet1/0/1] undo stp enable
[DeviceC-GigabitEthernet1/0/1] quit
[DeviceC] interface gigabitethernet 1/0/2
[DeviceC-GigabitEthernet1/0/2] undo stp enable
[DeviceC-GigabitEthernet1/0/2] quit
# Create smart link group 1 and configure all VLANs mapped to MSTIs 0 through 15 as the protected VLANs.
[DeviceC] smart-link group 1
[DeviceC-smlk-group1] protected-vlan reference-instance 0 to 15
# Configure GigabitEthernet 1/0/1 as the master port and GigabitEthernet 1/0/2 as the slave port.
[DeviceC-smlk-group1] port gigabitethernet1/0/1 master
[DeviceC-smlk-group1] port gigabitethernet1/0/2 slave
# Configure VLAN 1 as the transmit control VLAN.
[DeviceC-smlk-group1] flush enable
2) Configuration on Device E
# Disable STP on GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2.
<DeviceE> system-view
[DeviceE] interface gigabitethernet 1/0/1
[DeviceE-GigabitEthernet1/0/1] undo stp enable
[DeviceE-GigabitEthernet1/0/1] quit
[DeviceE] interface gigabitethernet 1/0/2
[DeviceE-GigabitEthernet1/0/2] undo stp enable
[DeviceE-GigabitEthernet1/0/2] quit
# Create smart link group 1 and configure all VLANs mapped to MSTIs 0 through 15 as the protected VLANs.
[DeviceE] smart-link group 1
[DeviceC-smlk-group1] protected-vlan reference-instance 0 to 15
# Configure GigabitEthernet 1/0/2 as the master port and GigabitEthernet 1/0/1 as the slave port.
[DeviceE-smlk-group1] port gigabitethernet1/0/2 master
[DeviceE-smlk-group1] port gigabitethernet1/0/1 slave
# Configure VLAN 1 as the transmit control VLAN.
[DeviceE-smlk-group1] flush enable
3) Configuration on Device B
# Configure VLAN 1 as the receive control VLAN for GigabitEthernet 1/0/1, GigabitEthernet 1/0/2, and GigabitEthernet 1/0/3.
<DeviceB> system-view
[DeviceB] interface gigabitethernet 1/0/1
[DeviceB-GigabitEthernet1/0/1] smart-link flush enable
[DeviceB-GigabitEthernet1/0/1] quit
[DeviceB] interface gigabitethernet 1/0/2
[DeviceB-GigabitEthernet1/0/2] smart-link flush enable
[DeviceB-GigabitEthernet1/0/2] quit
[DeviceB] interface gigabitethernet 1/0/3
[DeviceB-GigabitEthernet1/0/3] smart-link flush enable
4) Configuration on Device D
# Configure VLAN 1 as the receive control VLAN for GigabitEthernet 1/0/1, GigabitEthernet 1/0/2, and GigabitEthernet 1/0/3.
<DeviceD> system-view
[DeviceD] interface gigabitethernet 1/0/1
[DeviceD-GigabitEthernet1/0/1] smart-link flush enable
[DeviceD-GigabitEthernet1/0/1] quit
[DeviceD] interface gigabitethernet 1/0/2
[DeviceD-GigabitEthernet1/0/2] smart-link flush enable
[DeviceD-GigabitEthernet1/0/2] quit
[DeviceD] interface gigabitethernet 1/0/3
[DeviceD-GigabitEthernet1/0/3] smart-link flush enable
5) Configuration on Device A
# Configure VLAN 1 as the receive control VLAN for GigabitEthernet 1/0/1, GigabitEthernet 1/0/2, and GigabitEthernet 1/0/3.
<DeviceA> system-view
[DeviceA] interface gigabitethernet 1/0/1
[DeviceA-GigabitEthernet1/0/1] smart-link flush enable
[DeviceA-GigabitEthernet1/0/1] quit
[DeviceA] interface gigabitethernet 1/0/2
[DeviceA-GigabitEthernet1/0/2] smart-link flush enable
After completing the configuration, you can use the display command to verify the smart link configuration and view flush message statistics.
As shown in Figure 1-3:
l The traffic of VLAN 1 through VLAN 200 on Device C are dually uplinked to Device A by Device B and Device D. Implement load sharing to uplink the traffic of VLAN 1 through VLAN 100 and the traffic of VLAN 101 through VLAN 200 over different links to Device A.
l Implement dual link backup on Device C: the traffic of VLANs 1 through 100 (mapped to MSTI 0) is uplinked to Device A by Device B; the traffic of VLANs 101 through 200 (mapped to MSTI 2) is uplinked to Device A by Device D. Smart link group 1 references MSTI 0, and smart link group 2 references MSTI 2.
l The control VLAN of smart link group 1 is VLAN 10 and that of smart link group 2 is VLAN 101.
Figure 1-3 Multiple smart link groups load sharing configuration
1) Configuration on Device C
# Create VLANs and configure VLAN-to-MSTI mappings.
<DeviceC> system-view
[DeviceC] vlan 1 to 200
[DeviceC] stp region-configuration
[DeviceC-mst-region] instance 0 vlan 1 to 100
[DeviceC-mst-region] instance 2 vlan 101 to 200
[DeviceC-mst-region] active region-configuration
[DeviceC-mst-region] quit
# Disable STP on the ports, configure the ports as trunk ports, and configure the ports to allow packets from VLAN 1 through 200 to pass through.
[DeviceC] interface gigabitethernet 1/0/1
[DeviceC-GigabitEthernet1/0/1] undo stp enable
[DeviceC-GigabitEthernet1/0/1] port link-type trunk
[DeviceC-GigabitEthernet1/0/1] port trunk permit vlan 1 to 200
[DeviceC-GigabitEthernet1/0/1] quit
[DeviceC] interface gigabitethernet 1/0/2
[DeviceC-GigabitEthernet1/0/2] undo stp enable
[DeviceC-GigabitEthernet1/0/2] port link-type trunk
[DeviceC-GigabitEthernet1/0/2] port trunk permit vlan 1 to 200
[DeviceC-GigabitEthernet1/0/2] quit
# Create smart link group 1.
[DeviceC] smart-link group 1
# Configure protected VLANs for smart link group 1.
[DeviceC-smlk-group1] protected-vlan reference-instance 0
# Configure GigabitEthernet 1/0/1 as the master port and GigabitEthernet 1/0/2 as the slave port.
[DeviceC-smlk-group1] port gigabitethernet1/0/1 master
[DeviceC-smlk-group1] port gigabitethernet1/0/2 slave
# Enable role preemption.
[DeviceC-smlk-group1] preemption mode role
# Configure VLAN 10 as the transmit control VLAN of smart link group 1.
[DeviceC-smlk-group-1] flush enable control-vlan 10
[DeviceC-smlk-group-1] quit
# Create smart link group 2.
[DeviceC] smart-link group 2
# Configure protected VLANs for smart link group 2.
[DeviceC-smlk-group2] protected-vlan reference-instance 2
# Configure GigabitEthernet 1/0/1 as the slave port and GigabitEthernet 1/0/2 as the master port.
[DeviceC-smlk-group2] port gigabitethernet1/0/1 slave
[DeviceC-smlk-group2] port gigabitethernet1/0/2 master
# Enable role preemption.
[DeviceC-smlk-group2] preemption mode role
# Configure VLAN 101 as the transmit control VLAN of smart link group 2.
[DeviceC-smlk-group2] flush enable control-vlan 101
2) Configuration on Device B
# Configure VLAN 10 and VLAN 101 as the receive control VLANs of GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2.
<DeviceB> system-view
[DeviceB] vlan 1 to 200
[DeviceB] interface gigabitethernet 1/0/1
[DeviceB-GigabitEthernet1/0/1] port link-type trunk
[DeviceB-GigabitEthernet1/0/1] port trunk permit vlan 1 to 200
[DeviceB-GigabitEthernet1/0/1] smart-link flush enable control-vlan 10 101
[DeviceB-GigabitEthernet1/0/1] quit
[DeviceB] interface gigabitethernet 1/0/2
[DeviceB-GigabitEthernet1/0/2] port link-type trunk
[DeviceB-GigabitEthernet1/0/2] port trunk permit vlan 1 to 200
[DeviceB-GigabitEthernet1/0/2] smart-link flush enable control-vlan 10 101
3) Configuration on Device D
# Configure VLAN 10 and VLAN 101 as the receive control VLANs of GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2.
<DeviceD> system-view
[DeviceD] vlan 1 to 200
[DeviceD] interface gigabitethernet 1/0/1
[DeviceD-GigabitEthernet1/0/1] port link-type trunk
[DeviceD-GigabitEthernet1/0/1] port trunk permit vlan 1 to 200
[DeviceD-GigabitEthernet1/0/1] smart-link flush enable control-vlan 10 101
[DeviceD-GigabitEthernet1/0/1] quit
[DeviceD] interface gigabitethernet 1/0/2
[DeviceD-GigabitEthernet1/0/2] port link-type trunk
[DeviceD-GigabitEthernet1/0/2] port trunk permit vlan 1 to 200
[DeviceD-GigabitEthernet1/0/2] smart-link flush enable control-vlan 10 101
4) Configuration on Device A
# Configure VLAN 10 and VLAN 101 as the receive control VLANs of GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2.
<DeviceA> system-view
[DeviceA] vlan 1 to 200
[DeviceA] interface gigabitethernet 1/0/1
[DeviceA-GigabitEthernet1/0/1] port link-type trunk
[DeviceA-GigabitEthernet1/0/1] port trunk permit vlan 1 to 200
[DeviceA-GigabitEthernet1/0/1] smart-link flush enable control-vlan 10 101
[DeviceA-GigabitEthernet1/0/1] quit
[DeviceA] interface gigabitethernet 1/0/2
[DeviceA-GigabitEthernet1/0/2] port link-type trunk
[DeviceA-GigabitEthernet1/0/2] port trunk permit vlan 1 to 200
[DeviceA-GigabitEthernet1/0/2] smart-link flush enable control-vlan 10 101
After completing the configuration, you can use the display command to verify the smart link configuration and view flush message statistics.
