I'm running virtualised lab with compact cluster installation.

I use sushy-emulator for Redfish OOBM functionalities.

By mistake I managed to configure exactly the same BareMetalHost's .spec.bmc.address for all nodes. In my case they're using exactly the same IP and port combination, for an instance the correct configuration looks as follows:

$ oc get bmh -o json | jq -r '.items[] | "(.metadata.name): (.spec.bmc.address)"'
master-0: redfish-virtualmedia://192.168.232.1:8000/redfish/v1/Systems/7308f6c7-ea2f-47aa-a5b9-3fa2ecf836b7
master-1: redfish-virtualmedia://192.168.232.1:8000/redfish/v1/Systems/8318c12f-e847-4e74-920a-35af4588f305
master-2: redfish-virtualmedia://192.168.232.1:8000/redfish/v1/Systems/77d88569-a92a-4f47-8351-271369cdf32d

but by mistake I made it:

$ oc get bmh -o json | jq -r '.items[] | "(.metadata.name): (.spec.bmc.address)"'
master-0: redfish-virtualmedia://192.168.232.1:8000/redfish/v1/Systems/77d88569-a92a-4f47-8351-271369cdf32d
master-1: redfish-virtualmedia://192.168.232.1:8000/redfish/v1/Systems/77d88569-a92a-4f47-8351-271369cdf32d
master-2: redfish-virtualmedia://192.168.232.1:8000/redfish/v1/Systems/77d88569-a92a-4f47-8351-271369cdf32d

As you can imagine fixing that was a bit of fun, especially due to lack of ability to update the address (please see https://issues.redhat.com/browse/METAL-359). 

I'm confused why we're not allowing to update the BMC address  but at the same time we're not verifying if it is unique across the cluster.