3199696 - Pv4/IPv6 dual-stack networking is enabled by default for your Kubernetes cluster starting in Kubernetes version 1.21

After Kubernetes cluster upgraded to version 1.21 and above, when you are fetching the localhost IP addresses, you will obtain both IPv4 and IPv6 address.

For example, when executing the following groovy script via HAC:

import java.net.InetAddress;
import java.net.NetworkInterface;
import java.util.Enumeration;

Enumeration<NetworkInterface> interfaces = NetworkInterface.getNetworkInterfaces();
while (interfaces.hasMoreElements()) {
    NetworkInterface network = interfaces.nextElement();
    Enumeration<InetAddress> addresses = network.getInetAddresses();
    while (addresses.hasMoreElements()) {
        InetAddress element = addresses.nextElement();
        if ( "localhost" == element.getHostName()){
          println  element.getHostName() + ":" + element.getHostAddress();
        }
    } 
}

You will see only IPv4 address printed in environment with Kubernetes cluster version lower than 1.21:

localhost:127.0.0.1

And you will see both of the IPv4 and IPv6 addresses printed in nvironment with Kubernetes cluster version 1.21 and above:

localhost:0:0:0:0:0:0:0:1%lo
localhost:127.0.0.1

CCV2

KBA , CEC-SCC-CLA-ENV-EMG , Environment Management , CEC-HCS-CCAZ-K8S , Kubernetes infrastructure , Product Enhancement