R3102-R3103-HP 6600/HSR6600 Routers High Availability Configuration Guide

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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. Smart Link has the following features:
 Dedicated to dual uplink networks.
 Subsecond convergence.
 Easy to configure.
Terminology
Smart link group
A smart link group consists of only two member ports: the primary and the secondary ports. Only one
port is active for forwarding at a time, and the other port is blocked and in standby state. When link
failure occurs on the active port due to port shutdown or the presence of unidirectional link, the
standby port becomes active and takes over, and the original active port transits to the blocked state.
As shown in Figure 28, GigabitEthernet 3/0/1 and GigabitEthernet 3/0/2 of Router C and
GigabitEthernet 3/0/1 and GigabitEthernet 3/0/2 of Router D each form a smart link group, with
GigabitEthernet 3/0/1 being active and GigabitEthernet 3/0/2 being standby.
Primary/secondary port
Primary port and secondary port are two port roles in a smart link group. When both ports in a smart
link group are up, the primary port preferentially transits to the forwarding state, and the secondary
port stays in standby state. Once the primary port fails, the secondary port takes over to forward
traffic. As shown in Figure 28, you can configure GigabitEthernet 3/0/1 of Router C and that of
Router D as primary ports, and GigabitEthernet 3/0/2 of Router C and that of Router D secondary
ports.
Primary/secondary link
The link that connects the primary port in a smart link group is the primary link; the link that connects
the secondary port is the secondary link.
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.
Protected VLAN
A smart link group controls the forwarding state of some data VLANs (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
devices (such as Router C and Router D in Figure 28) 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 devices (such as Router A, Router B, and Router E in Figure 28) receive and process flush