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In this section:


The Link Monitor object allows you to monitor a link for a specific interface and belongs to a link detection group. Link Monitor verifies transport on a specific interface via Layer 3 ICMP/ARP/NUD to a specific destination, or monitors the Media Independent Interface (MII) state for the physical port.

A new Link Monitor is created on an interface for link verification. The Link Monitor is provided with a destination to use for link verification as well as the Link Detection Group to which it belongs. The Link Monitor is responsible for pinging that destination, processing responses and determining when the interface should be considered failed. It reports such failures to its Link Detection Group. The active and standby SBC should be connected to different physical hardware (that is, switches) to avoid a single point of failure.

Each Link Monitor that is configured can also be configured with unique values for the Verify Timer, Response Timer, Reattempt Timer, and Retries. If configured, these values override the values configured for the Link Detection Group.

Each Link Monitor will set a timer while waiting to perform its next verification. The timeout for this timer is based on the configured Verify Timer value. When a ping is in progress and the Link Monitor is awaiting the response from the destination, a timer is set based on the configured Response Timer value. When the response times out and the Link Monitor retries, the Reattempt Timer value is used while waiting for the response.

When the number of consecutive failures reaches the Retries value, the Link Monitor considers the link verification as failed and reports this to its Link Detection Group.

While in the failed state, the Link Monitor will continue to attempt to ping the destination so that the failed condition can eventually clear. This is done at the rate specified by the Verify Timer.

The Link Monitor also supports a NULL destination (0.0.0.0), which disables the link verification for that interface. The interface is still considered failed if there is a hardware failure.

To View Link Monitor Objects

On the SBC main screen, go to Configuration > System Provisioning > Category: Base Provisioning > Link Detection Group > Link Monitor. The Link Monitor window opens. Use the drop-down lists to filter by Address Context and Link Detection Group. 

Note:

The columns that appear in this window and the configuration options available for the Link Monitor object depend on your environment. See the Link Monitor parameter table for the dependencies.

Link Monitor

 

To Create a Link Monitor 

To create a new Link Monitor:

  1. Select the Address Context and Link Detection Group with which you want to associate the Link Monitor. The option to create a Link Monitor becomes available.

  2. Click New Link Monitor. The Create New Link Monitor window is displayed. 

    Create New Link Monitor Window - Example

     
  3. Use the following table to enter values and click Save.

Link Monitor Parameters


Parameter

Description

Name

Specifies the name of this Link Monitor.

Physical Port

Physical port associated with the IP interface to be monitored. In a redundancy configuration, pkt0P is paired with pkt0S and pkt1P is paired with pkt1S.

  • pkt0P – Primary packet 0 port.
  • pkt0S – Secondary packet 0 port.
  • pkt1P – Primary packet 1 port.
  • pkt1S – Secondary packet 1 port.


Note

This parameter is only visible on SBC 7000 systems and D-SBC systems on OpenStack with support for packet port redundancy (must have four packet ports configured). 


IP Interface GroupSpecifies the name of the IP Interface Group to be monitored.
IP Interface

Specifies the name of the IP or management interface to be monitored.

Note

IP or MGMT interface can be configured, depending on the type that is configured for the Link Detection Group.

Destination

Specifies the destination IP address for link verification.

Note

The Destination IP address must be within the same subnet as the source interface.

Verify Timer

Specifies the time interval (in milliseconds) between link verification attempts.

Response Timer

Specifies the time to wait (in milliseconds) for a response to a link verification attempt.

Reattempt
Timer

Specifies the time to wait (in milliseconds) for a response to a link verification re-attempt.

Retries

Specifies the number of retries before the link verification is considered failed.

State

Specifies the administrative state for this Link Monitor.

Probe On Standby

Use this option to enable/disable probing of the standby port for the specified Link Monitor.

  • Disabled – Use this option to disable probing of the standby port when the router does not respond properly to the ARP/NUD probes, such as scenarios where the destination router does not support RFC5227 and cannot reply to the ARP probe. For additional details, see the "Link Detection Support" topic in SBC Core Redundancy (SBC 7000) or SBC SWe Port Redundancy and Link Detection in OpenStack Cloud Deployments (D-SBC on OpenStack).
  • Enabled (default) – Use this option to allow probing of the standby port.

NOTE: This flag is only visible on SBC 7000 systems and D-SBC systems on Openstack with 4 packet ports.

Probe On Standby SWe

Use this option to enable/disable probing of the standby port for the specified Link Monitor on SBC SWe systems with two packet ports.

  • Disabled – Use this option to disable probing of the standby port when the router does not respond properly to the ARP/NUD probes, such as scenarios where the destination router does not support RFC5227 and cannot reply to the ARP probe. For additional details, see the "Link Detection Support" topic in SBC SWe Port Redundancy and Link Detection in OpenStack Cloud Deployments.
  • Enabled (default) – Use this option to allow probing of the standby port.

NOTE: This flag is only visible on SBC SWe systems with 2 packet ports.

Bfd ProfileThe name of the BFD profile to associate with this Link Monitor configuration to monitor links on active ports.
Note

 If the Link Detection Group should take precedence over Link Monitoring, delete the timers from the Link Monitor configuration.

To Edit a Link Monitor

To edit any of the Link Monitors in the list:

  1. Click the radio button next to the specific Link Monitor name. The Edit Selected Link Monitor window opens.
  2. Make the required changes and click Save.

To Copy a Link Monitor

To copy any of the Link Monitors in the list:

  1. Click the radio button next to the specific Link Monitor to copy.
  2. Click Copy Link Monitor. The Copy Selected Link Monitor window opens.
  3. Make the required changes and click Save.

To Delete a Link Monitor

To delete any of the Link Monitors in the list: 

  1. Click the radio button next to the specific Link Monitor to delete.
  2. Click the delete icon (X) at the end of the row.
  3. Confirm the deletion when prompted.