The packet duplication feature can be used to mitigate packet loss. Packet duplication duplicates packets on alternate available SD-WAN tunnels.

Receiving Cisco IOS XE Catalyst SD-WAN devices forward one packet to the server and discard the duplicate packets.

Packet duplication is suitable for edges with multiple WAN links.

You can view the tunnel packet duplication statistics using device CLI or the Cisco SD-WAN Manager device dashboard.

Note	From Cisco IOS XE Catalyst SD-WAN Release 17.18.1a, the tunnel selection algorithm has been optimized. While selecting a duplicate tunnel, the highest preference is given to the tunnel which has a different local color compared to that of the primary tunnel.

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.

Minimum supported release: Cisco Catalyst SD-WAN Control Components Release 20.14.1

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.

Minimum supported releases: Cisco IOS XE Catalyst SD-WAN Release 17.15.1a

1. From the Cisco SD-WAN menu, choose Configuration > Configuration Groups.

2. Click Transport & Management Profile.

3. Select the desired transport profile and click Edit.

4. Click Edit Ethernet Interface > Tunnel.

5. Enable Allow Fragmentation and MTU To Max.

6. Click Save.

• Packet duplication interop, forward error correction (FEC), and TCP optimization on Cisco IOS XE Catalyst SD-WAN devices is not supported between Cisco IOS XE Release 16.x and Cisco IOS XE Catalyst SD-WAN Release 17.x versions.

• Packet duplication cannot work in conjunction with local or remote TLOC in the policy. Data policy or AAR is not configured when specifying the packet duplicated tunnel.

• Packet duplication is supported only on Cisco IOS XE Catalyst SD-WAN devices but not on all the edge devices.

The following is sample output from the show sdwan tunnel statistics pkt-dup command:

Device#show sdwan tunnel statistics pkt-dup
tunnel stats ipsec 192.0.2.1 203.0.113.1 12366 12406
pktdup-rx                           1313388
pktdup-rx-other                     526666
pktdup-rx-this                      1324958
pktdup-rx-fwd                       540190
pktdup-rx-fwd-dup-tun               789569
pktdup-tx                           0
pktup-tx-other                      0
pktdup-tx-dup-tun-selection-failed  0
pktdup-tx-dup-tun-sent-failed       0
pktdup-capable                      true