Smart Link

Introduction

Smart link is a switch feature that provides effective, simple and fast-converging link redundancy in network topology with dual uplink between different layers of the network. It requires an active (master) and a backup (slave) link. The active link carries the uplink traffic. Upon failure of the active link, a switchover is triggered and the traffic is directed to the backup link.

In the previous figure, ports A1 and A2 are configured as part of a Smart link group. The connection from the access switch to Distribution Switch A is the master, and the connection from the access switch to Distribution Switch B is the slave.
Only the master interface forwards traffic for a group of VLANs (referred to as protected VLAN group).
The other interface is in standby mode for this protected group. If port A1 goes down, port A2 starts forwarding traffic for this protected VLAN group.
If port A1 comes back up, it goes to standby mode and does not forward traffic. Port A2 continues forwarding traffic. This is the case if preemption-mode is configured as “role”.If preemption-mode is not configured as “role”, when the master (A1) comes back up, it becomes Active (forwarding) after the configured ‘preemption-delay’.
Since a Smart link group has the information readily available via configuration as to which port should be forwarding for the protected VLAN group in the case of the active link failure, the failover is much quicker when compared with STP.

Configuring Smart Link

Use the following commands to configure Smart link:

Create a smart link group, using optional parameters as necessary:

HP-Switch(config)#[no] smart-link group group-id

Options

master port

slave port

protected-vlans vid-list

send-control-vlan vid

preemption-mode off | forced | bandwidth

preemption-delay 10...max

trap enable | disable

NOTE: When executed without any parameters, this command enters into Smart link group context.
Configure VLANs to receive flush messages. This is an interface level command. It must be executed for both the master and the slave port.

HP-Switch(config)# smart-link recv-control-vlan vid-list

Enable debug messages for a Smart link group:

HP-Switch(config)#debug smart-link [ group group-id | all ] [flush-packets]

Configuration example

The following example illustrates Smart link configuration with VLAN load-balancing:

vlans 1-10 mapped to smart-link group 1:

HP-Switch(config)#smart-link group 1 master a1 slave a2
HP-Switch(config)#smart-link group 1 protected-vlans 1-10
HP-Switch(config)#smart-link group 1 send-control-vlan 1
HP-Switch(config)#smart-link group 1 preemption-mode role
HP-Switch(config)#smart-link group 1 preemption-delay 10

vlans 11-20 mapped to smart-link group 2:

HP-Switch(config)#smart-link group 2 master a2 slave a1
HP-Switch(config)#smart-link group 2 protected-vlans 11-20
HP-Switch(config)#smart-link group 2 send-control-vlan 10
HP-Switch(config)#smart-link group 2 preemption-mode role
HP-Switch(config)#smart-link group 2 preemption-delay 15

Viewing Smart Link information

Smart link supports the following show commands:

Show the Smart link group information. Detailed output is displayed if group is specified, otherwise only basic information is displayed for all groups.

show smart-link group { group-id | all }

The H3C-equivalent display command is:

display smart-link group [ group-id | all ] [ begin | exclude | include ] regular-expression
Show statistics of received flush packets

show smart-link flush-statistics

The H3C-equivalent display command is:

display smart-link flush [ begin | exclude | include ] regular-expression
Show receive control VLANs configured on per port basis:

show smart-link recv-control-vlans

Clearing statistics

Use the following command to clear group and flush statistics

clear smart-link [flush-statistics] [ group group-id | all ]

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	NOTE: When executed without any parameters, this command enters into Smart link group context.