"No route to host"

I am responsible for maintaining our VPN software, the server and client debugging, everything goes smoothly,The default routing I've been using before,but today there is a need to divert the data flow of the client, I found that it can be achieved through includeroutes, so I set up 10.20.0.1/4, so the network segment will go through the tunnel, magical things happen, data transmission failure, the server did not receive data packets.


Error reporting information is:

Error Domain=NSPOSIXErrorDomain Code=65 "No route to host"


I suspect that the data is sent to the virtual network card and the corresponding route is not found to reach the real network card, which leads to the failure of data transmission. What is the situation?