1. Proposed title of this feature request : Support for DNS resolution of Services via Primary User Defined Network (UDN) IPs

2. What is the nature and description of the request?

Problem Statement: Currently, when using User Defined Networks (UDN) in OpenShift (OCP), Pods are assigned IP addresses from the UDN subnet. However, DNS resolution for Services still returns the ClusterIP or IP address from the default cluster network (provided by the default CNI). This behavior forces traffic intended for isolated UDNs to route through the default network, which compromises full network isolation and makes Service discovery within a UDN non-intuitive for users.

Requirement: Implement a mechanism where CoreDNS/Service resolution returns the IP address associated with the Primary UDN. This would allow Pods to communicate with Services entirely via the udn-0 interface (or the primary UDN interface), removing the dependency on the default cluster network for Service discovery and data plane traffic.

Target Use Cases:

• Service Resolution: Ensure that standard Service queries return the udn-0 assigned IP address instead of the default cluster network IP.

• Headless Service Resolution: Ensure that DNS queries for Headless Services return the udn-0 Pod IPs, allowing for direct Pod-to-Pod communication within the isolated network.

3. Why does the customer need this? (List the business requirements here)

Part of PoC

4. List any affected packages or components. : UDN, DNS