LAN IP showing up on WAN MAC on my core switch

[woncom]

Closest I can get in the forums for this behavior is from 2016 at this post:

ISP Modem seeing internal LAN IP Addresses with WAN-1 MAC IDs

Another datapoint on that. I am experiencing some issues with cable modems denying internet access to the Peplink SOHO, and while I still haven’t been able to confirm the problem here is the issue, I do see some local LAN ARP broadcasts on the WAN port, including Local LAN IPs and MAC addresses of devices behind the NAT firewall. Those devices should not be visible on the WAN port and those ARP should be dropped on the WAN, but according to the capture logs it is possible these are being forward…

I am an ISP and using peplink for my business customers. I recently had an issue where traffic found its way out my customers gateway over FusionHub because my switch seen the LAN IP as a valid gateway. Example image posted here shows on my switch where the LAN IP shares the WAN MAC and is broadcast across the network.

How can I kill this behavior?

[Oh_Yaw_Theng]

Can you open up a ticket for this here ? We can help to check and investigate.