Hello,

I am using the library in an IPv6 environment. At some point, I have some router advertisements (RAs) that change the preferred prefix on the interface from where the requests are sent. The old IPv6 value that was set as the source for address for my requests is invalidated and at some point removed. The requests are continued to be sent with the old address since I'm trying to reuse it. The request is not succeeding, but coap_send is not returning COAP_INVALID_MID either. However, if I set an IPv4 as my source address for the requests, I see that coap_send returns COAP_INVALID_MID and there are also logs like these:

coap_socket_send: Network is unreachable
*  10.42.0.1:39516 <-> 10.42.0.1:5683 UDP : netif: failed to send 25 bytes (Network is unreachable) state 4

The behavior can be observed with both confirmable and non-confirmable requests.
Has anyone else encountered this?

Thank you!