Network about rancher 1.6

Hello,
We are using rancher 1.6 and our environment is the default Cattle template. I met a lots of questions. I have two containers which are two applications with the same public IP with differrent port,both of them are in the same rancher environment and netwok. Now I use a container A with publish IP as a sender to ask request to another container B. In container B , I print the ip of the sender, It is surprised me that I saw the internal container ip of container A ranther than the public IP. So I want to ask you whether this phenomenon is normal ,Can you tell me the reason ?