When adding new nodes to the existing cluster, the newly allocated node-subnet can be overlapped with the existing node.

openshift 4.10.30

It's quite hard to reproduce but  there is a possibility it can happen any time. 

1. Create a OVN dual-stack cluster
2. add nodes to the existing cluster
3. check the allocated node subnet 

Some newly added nodes have the same node-subnet and ovn-k8s-mp0 IP as some existing nodes.

Should have duplicated node-subnet and ovn-k8s-mp0 IP

Additional info can be found at the case 03329155 and the must-gather attached(comment #1) 

% omg logs ovnkube-master-v8crc -n openshift-ovn-kubernetes -c ovnkube-master | grep '2022-09-30T06:42:50.857'
2022-09-30T06:42:50.857031565Z W0930 06:42:50.857020       1 master.go:1422] Did not find any logical switches with other-config
2022-09-30T06:42:50.857112441Z I0930 06:42:50.857099       1 master.go:1003] Allocated Subnets [10.131.0.0/23 fd02:0:0:4::/64] on Node worker01.ss1.samsung.local
2022-09-30T06:42:50.857122455Z I0930 06:42:50.857105       1 master.go:1003] Allocated Subnets [10.129.4.0/23 fd02:0:0:a::/64] on Node oam04.ss1.samsung.local
2022-09-30T06:42:50.857130289Z I0930 06:42:50.857122       1 kube.go:99] Setting annotations map[k8s.ovn.org/node-subnets:{"default":["10.131.0.0/23","fd02:0:0:4::/64"]}] on node worker01.ss1.samsung.local
2022-09-30T06:42:50.857140773Z I0930 06:42:50.857132       1 kube.go:99] Setting annotations map[k8s.ovn.org/node-subnets:{"default":["10.129.4.0/23","fd02:0:0:a::/64"]}] on node oam04.ss1.samsung.local
2022-09-30T06:42:50.857166726Z I0930 06:42:50.857156       1 master.go:1003] Allocated Subnets [10.128.2.0/23 fd02:0:0:5::/64] on Node oam01.ss1.samsung.local
2022-09-30T06:42:50.857176132Z I0930 06:42:50.857157       1 master.go:1003] Allocated Subnets [10.131.0.0/23 fd02:0:0:4::/64] on Node rhel01.ss1.samsung.local
2022-09-30T06:42:50.857176132Z I0930 06:42:50.857167       1 kube.go:99] Setting annotations map[k8s.ovn.org/node-subnets:{"default":["10.128.2.0/23","fd02:0:0:5::/64"]}] on node oam01.ss1.samsung.local
2022-09-30T06:42:50.857185257Z I0930 06:42:50.857157       1 master.go:1003] Allocated Subnets [10.128.6.0/23 fd02:0:0:d::/64] on Node call03.ss1.samsung.local
2022-09-30T06:42:50.857192996Z I0930 06:42:50.857183       1 kube.go:99] Setting annotations map[k8s.ovn.org/node-subnets:{"default":["10.131.0.0/23","fd02:0:0:4::/64"]}] on node rhel01.ss1.samsung.local
2022-09-30T06:42:50.857200017Z I0930 06:42:50.857190       1 kube.go:99] Setting annotations map[k8s.ovn.org/node-subnets:{"default":["10.128.6.0/23","fd02:0:0:d::/64"]}] on node call03.ss1.samsung.local
2022-09-30T06:42:50.857282717Z I0930 06:42:50.857258       1 master.go:1003] Allocated Subnets [10.130.2.0/23 fd02:0:0:7::/64] on Node call01.ss1.samsung.local
2022-09-30T06:42:50.857304886Z I0930 06:42:50.857293       1 kube.go:99] Setting annotations map[k8s.ovn.org/node-subnets:{"default":["10.130.2.0/23","fd02:0:0:7::/64"]}] on node call01.ss1.samsung.local
2022-09-30T06:42:50.857338896Z I0930 06:42:50.857314       1 master.go:1003] Allocated Subnets [10.128.4.0/23 fd02:0:0:9::/64] on Node f501.ss1.samsung.local
2022-09-30T06:42:50.857349485Z I0930 06:42:50.857329       1 master.go:1003] Allocated Subnets [10.131.2.0/23 fd02:0:0:8::/64] on Node call02.ss1.samsung.local
2022-09-30T06:42:50.857371344Z I0930 06:42:50.857354       1 kube.go:99] Setting annotations map[k8s.ovn.org/node-subnets:{"default":["10.128.4.0/23","fd02:0:0:9::/64"]}] on node f501.ss1.samsung.local
2022-09-30T06:42:50.857371344Z I0930 06:42:50.857361       1 kube.go:99] Setting annotations map[k8s.ovn.org/node-subnets:{"default":["10.131.2.0/23","fd02:0:0:8::/64"]}] on node call02.ss1.samsung.local