Description of problem:

nodePort with different network and different node after advertisement,  ipv4:nodePort can work  but ipv6:nodePort not

1 we have two CUDN and two namespace 

# oc get net-attach-def -n z7
NAME   AGE
blue   33h
# oc get net-attach-def -n z8
NAME   AGE
red    30h

2.  there is nodePort svc with ETP=Cluster in namespace z7

# oc get pod -n z7
NAME            READY   STATUS    RESTARTS   AGE
test-rc-8cn7f   1/1     Running   0          33h
test-rc-fjvb9   1/1     Running   0          33h


# oc get svc hello-pod -n z7 -o yaml
apiVersion: v1
kind: Service
metadata:
  creationTimestamp: "2025-04-16T04:15:42Z"
  labels:
    name: hello-pod
  name: hello-pod
  namespace: z7
  resourceVersion: "1245272"
  uid: 83256f76-2b6f-41e7-bc4b-0a6707a8828a
spec:
  clusterIP: 172.30.86.22
  clusterIPs:
  - 172.30.86.22
  - fd02::da8a
  externalTrafficPolicy: Cluster
  internalTrafficPolicy: Cluster
  ipFamilies:
  - IPv4
  - IPv6
  ipFamilyPolicy: PreferDualStack
  ports:
  - name: http
    nodePort: 32704
    port: 27017
    protocol: TCP
    targetPort: 8080
  selector:
    name: test-pods
  sessionAffinity: None
  type: NodePort
status:
  loadBalancer: {}
 

  3 . Before advertise CUDN,  ipv4 and ipv6 are working except same node which is expected

# oc rsh -n z8 test-rc-w4c2q
~ $ curl 192.168.111.23:32704
Hello OpenShift!
~ $ curl 192.168.111.24:32704
Hello OpenShift!
~ $ curl 192.168.111.25:32704     ###same node is not working, expected
^C
~ $ curl 192.168.111.25:32704^C
~ $ curl [fd2e:6f44:5dd8:c956::17]:32704
Hello OpenShift!
~ $ curl [fd2e:6f44:5dd8:c956::18]:32704
Hello OpenShift!
~ $ curl [fd2e:6f44:5dd8:c956::19]:32704
^C
 

4.  After advertise cudn

# oc get ra
NAME      STATUS
cudn      Accepted
 

5.   one issue is ipv4 still working with different node and different network, but ipv6 cannot

      another issue is same node ipv4 and ipv6 became working. 

# oc rsh -n z8 test-rc-w4c2q
~ $ 
~ $ curl 192.168.111.23:32704
Hello OpenShift!
~ $  curl 192.168.111.24:32704
Hello OpenShift!
~ $  curl 192.168.111.25:32704
Hello OpenShift!
~ $ curl [fd2e:6f44:5dd8:c956::17]:32704
^C
~ $ curl [fd2e:6f44:5dd8:c956::18]:32704
^C
~ $ 
~ $ curl [fd2e:6f44:5dd8:c956::19]:32704
Hello OpenShift!
 

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:

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Additional info:

Please fill in the following template while reporting a bug and provide as much relevant information as possible. Doing so will give us the best chance to find a prompt resolution.

Affected Platforms:

Is it an

1. internal CI failure
2. customer issue / SD
3. internal RedHat testing failure

If it is an internal RedHat testing failure:

• Please share a kubeconfig or creds to a live cluster for the assignee to debug/troubleshoot along with reproducer steps (specially if it's a telco use case like ICNI, secondary bridges or BM+kubevirt).

If it is a CI failure:

• Did it happen in different CI lanes? If so please provide links to multiple failures with the same error instance
• Did it happen in both sdn and ovn jobs? If so please provide links to multiple failures with the same error instance
• Did it happen in other platforms (e.g. aws, azure, gcp, baremetal etc) ? If so please provide links to multiple failures with the same error instance
• When did the failure start happening? Please provide the UTC timestamp of the networking outage window from a sample failure run
• If it's a connectivity issue,
• What is the srcNode, srcIP and srcNamespace and srcPodName?
• What is the dstNode, dstIP and dstNamespace and dstPodName?
• What is the traffic path? (examples: pod2pod? pod2external?, pod2svc? pod2Node? etc)

If it is a customer / SD issue:

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• Don’t presume that Engineering has access to Salesforce.
• Do presume that Engineering will access attachments through supportshell.
• Describe what each relevant attachment is intended to demonstrate (failed pods, log errors, OVS issues, etc).
• Referring to the attached must-gather, sosreport or other attachment, please provide the following details:
  • If the issue is in a customer namespace then provide a namespace inspect.
  • If it is a connectivity issue:
    • What is the srcNode, srcNamespace, srcPodName and srcPodIP?
    • What is the dstNode, dstNamespace, dstPodName and dstPodIP?
    • What is the traffic path? (examples: pod2pod? pod2external?, pod2svc? pod2Node? etc)
    • Please provide the UTC timestamp networking outage window from must-gather
    • Please provide tcpdump pcaps taken during the outage filtered based on the above provided src/dst IPs
  • If it is not a connectivity issue:
    • Describe the steps taken so far to analyze the logs from networking components (cluster-network-operator, OVNK, SDN, openvswitch, ovs-configure etc) and the actual component where the issue was seen based on the attached must-gather. Please attach snippets of relevant logs around the window when problem has happened if any.

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