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CX11x, CX31x, CX710 (Earlier Than V6.03), and CX91x Series Switch Modules V100R001C10 Configuration Guide 12

The documents describe the configuration of various services supported by the CX11x&CX31x&CX91x series switch modules The description covers configuration examples and function configurations.
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Introduction to Smart Link and Monitor Link

Introduction to Smart Link and Monitor Link

This section describes the concepts and functions of Smart Link and Monitor Link.


Smart Link is a link backup feature. A Smart Link group consists of two interfaces. One interface is the backup of the other. Smart Link is often used in dual-homing networking to implement link backup and rapid switchover.

Monitor Link monitors a device uplink interface and triggers the downlink interface status change according to the uplink interface status, which triggers switching of a topology protocol on the downstream device.


When a device connects to an upstream device through a single uplink, services are interrupted if a single point failure occurs. In dual-homing networking, a downstream device is connected to two upstream devices to reduce impact of single point failures and improve network reliability.

Figure 11-69 Smart Link in dual-homing networking

As shown in Figure 11-69, SwitchA is connected to SwitchB and SwitchC in dual-homing mode. Therefore, two links are available from SwitchA to SwitchD: SwitchA -> SwitchB -> SwitchD and SwitchA -> SwitchC -> SwitchD. Network loops may cause broadcast storms. Smart Link is configured on SwitchA. Normally, the link of Interface1 transmits traffic, and the link of Interface2 is a backup link. If the link of Interface1 fails, Smart Link automatically switches all the data traffic to the link of Interface2, ensuring nonstop service transmission.

Smart Link has following advantages:
  • Prevents broadcast storms caused by loops. When two links are running properly in dual-homing networking, only one link transmits traffic and the other link is blocked.
  • Is easy to configure and use.
  • Ensures data forwarding. When the active link is faulty, traffic is switched to the standby link in milliseconds.

On some networks where Layer 2 topology protocols such as Smart Link are used, topology protocols cannot monitor the uplink interface status. As a result, services cannot be switched. Monitor Link monitors the uplink interface status of a device and changes the downlink interface status according to the uplink interface status, which triggers switching of a topology protocol on the downstream device. Monitor Link prevents traffic loss caused by the uplink fault.

Updated: 2019-08-09

Document ID: EDOC1000041694

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