If I remember, It’s expected behavior for only one interface to respond to pings if multiple interfaces have IPs on the same subnet. FreeRTOS-Plus-TCP’s current routing logic selects the first matching endpoint, making only one effectively reachable. To ping both, ensure they are on different subnets
Here is the documentation: FreeRTOS-Plus-TCP Multiple Interfaces - FreeRTOS
Some notes from the documentation:
Two networks, same network address
Some users on the FreeRTOS forum have asked if two networks may have the same network address. The algorithm says that the first interface with a matching network address shall be used. The same for an incoming TCP connection: the very first SYN packet will set the MAC-address and the interface used. As for UDP packets: incoming packets will be replied to through the interface that received the packet.