Does the VSP platform offer any way to migrate from one I-SID to another I-SID?
The intended use case would be for engineers that inherit an environment that they would like to standardize, or if there was an issue with an out of order I-SID scheme.
I think the easiest way to do this would be to add some form of secondary I-SID functionality that way all BEB/BCB can pre-compute their connections for the given I-SID, which would then allow you to gracefully migrate all nodes off of the primary without service interruption?
Not really.. this is a feature request. You probably need a brief down time to swap an I-SID. With NAC it would be easier, as you can change the RADIUS returned I-SID and then just re-authenticate all devices.