Cisco Catalyst SD-WAN Policies Configuration Guide, Releases 26.x and Later

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Configure packet duplication

Updated: April 24, 2026

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Configure packet duplication using policy groups

Configure packet duplication through policy groups to enhance network reliability by creating duplicate packets for critical traffic flows.

Packet duplication is a loss correction technique that sends duplicate copies of packets across different paths to ensure reliable delivery of critical network traffic. This feature is available starting from Cisco Catalyst SD-WAN Control Components Release 20.14.1.

Procedure

1.

Select Configuration > Policy Groups.
2.

Click Application Priority & SLA.
3.

Click Add Application Priority & SLA Policy.

Provide a policy name and description.
4.

Enable Advanced Layout in the top right pane.
5.

Click Add Traffic Policy.
6.

Enter a name for the policy and specify VPNs.
7.

In the Direction drop-down list, select All.
8.

In the Default Action, click Accept.
9.

Click Add.
10.

Click Add Rules.
11.

Click Match.

Select appropriate match condition.
12.

Click Action > Loss Correction.
13.

In the Type drop-down list, choose Packet Duplication.
14.

Click Save Match and Actions.
15.

Click Save Policy.

The packet duplication policy is configured and applied to the specified traffic flows, providing loss correction through duplicate packet transmission.

Configure packet duplication on additional tunnels using the CLI

When packet duplication is enabled, by default, packets are duplicated on one additional tunnel. Using the packet-duplication max-preselect<2-4> command, you can enable duplication on 2-4 additional tunnels.

Before you begin

If you do not configure this command, the duplication factor remains 1 by default.

This configuration only configures the duplication number. The actual duplication is enabled using the policy configuration method.

Procedure

Configure the duplication number.

Example:

config-tr
    sdwan
     packet-duplication max-preselect <2-4>

Configure packet duplication using classic policies

Configure packet duplication to reduce packet loss by duplicating packets and sending them on the next available links.

Use classic policies to configure packet duplication for applications that require enhanced reliability and reduced packet loss. This feature is configured through centralized policies in Cisco SD-WAN Manager.

Procedure

1.

From the Cisco SD-WAN Manager menu, choose Configuration > Policies.
2.

Select Centralized Policy at the top of the page and then click Add Policy.
3.

Click Next twice to select Configure Traffic Rules.
4.

Select Traffic Data, and from the Add Policy drop-down list, click Create New.
5.

Click Sequence Type in the left pane.
6.

From the Add Data Policy pop-up window, select QoS.
7.

Click Sequence Rule.
8.

In the Applications/Application Family List/Data Prefix, select one or more applications or lists.
9.

Click Actions and choose Loss Correction.
10.

In the Actions area, select the Packet Duplication option to enable the packet duplication feature.

  • FEC Adaptive: Only send Forward Error Correction (FEC) information when the system detects a packet loss.

  • FEC Always: Always send FEC information with every transmission.

  • None: Use when no loss protection is needed.

  • Packet Duplication: Enable when packets need to be duplicated and sent on the next available links to reduce packet loss.
11.

Click Save Match and Actions.
12.

Click Save Data Policy.
13.

Click Next and take these actions to create a Centralized Policy:

  1. Enter a Name and a Description.

  2. Select Traffic Data Policy.

  3. Choose VPNs/site list for the policy.

  4. Save the policy.

The packet duplication policy is configured and applied to the selected applications and VPNs. Packets for the specified applications will be duplicated and transmitted over multiple links to reduce packet loss.