Topology: ER8411 in a multi-WAN configuration.

• WAN1: Xfinity (public IP)

• WAN2: Xfinity (public IP)

• WAN3: Starlink (CGNAT IP)

Description of Bug

The DDNS client on the Omada ER8411 is incorrectly updating the hostname for a WAN port that has a Carrier-Grade NAT (CGNAT) IP address. Instead of reporting its own WAN IP, the DDNS client sends the public IP address of another WAN port in the multi-WAN configuration.

Steps to Reproduce

1. Connect and configure three WAN interfaces: two with public IP addresses (e.g., from Xfinity) and one with a CGNAT IP address (e.g., from Starlink, IP range 100.64.0.0/10).

2. Enable DDNS for each WAN port, using a DDNS service such as NO-IP.

3. Ensure each DDNS entry is explicitly bound to its respective WAN port in the Omada Controller settings.

4. Observe the IP address reported in the DDNS service provider's dashboard for each hostname.

Observed Behavior

The DDNS hostname for the Starlink WAN port (WAN3) is updated with the public IP address of one of the Xfinity WAN ports. This results in one Xfinity public IP being duplicated in the NO-IP dashboard, and the Starlink DDNS hostname is useless for remote access as it points to the wrong ISP.

This behavior occurs despite the DDNS entry for WAN3 being explicitly configured and bound to the Starlink interface. The router's internal DDNS update process seems to be ignoring the WAN interface binding and is instead routing the update request out of a different, public-facing WAN port.

Expected Behavior

• The DDNS hostname for WAN1 should be updated with the public IP address of WAN1.

• The DDNS hostname for WAN2 should be updated with the public IP address of WAN2.

• The DDNS hostname for WAN3 (Starlink) should be updated with the private CGNAT IP address of WAN3 (100.120.37.1). This is expected behavior for a CGNAT connection, as the DDNS service will correctly report the IP of the WAN port that sends the update request, even if it's not a publicly-routable IP. The key issue is that the update is being sent from the wrong port.

Workaround Attempted

I have attempted to verify that each DDNS entry is correctly configured to its WAN port, but the issue persists. A potential workaround is to use Policy-Based Routing to force the DDNS update traffic from the router to exit through the correct WAN port, but this is a complex solution for what appears to be a bug in the DDNS client logic.

Request

Please investigate this issue as it appears to be a significant bug in the DDNS implementation on the ER8411 in multi-WAN environments. This behavior has been reported by other users and impacts the functionality of multi-WAN DDNS. A permanent fix in a future firmware update is requested.