The cluster UUID is universally unique, as per the standard definition of "UUID", and the cluster serial number SHOULD be unique - but it isn't. We only hand them out to a single customer, but it isn't node-locked and can be used in multiple clusters.
The cluster serial is set based on the cluster base license key entered. It sometimes happens with conversions, rushed installs etc, that the cluster base license key is unavailable, and a well known temporary key is used which corresponds to serial 180000099, so you will sometimes see customers with multiple clusters with the serial 180000099. The cluster serial number can be changed if necessary.
We have develeoped a system and were using "Cluster Serial Number" to identify the cluster. Later we realised that it is not uniqe across clusters. COuld you please share the steps to change the "Cluster Serial Number"?
To change the cluster serial number, obtain a proper cluster base license code for the system, either by looking up the sales order number for the first two nodes serial numbers on the support-licenses site, and then looking up licenses by sales order number, or by obtaining one through your NetApp account rep, and add it with "license add". Once added, remove the original cluster base license.