Officially, you have to remove it and re-add it. This has been true for all versions of vCloud Director.
Please understand the below is not officially supported.
If you are looking into the database, it's probably IP_scope you are looking for. Locate your scope and update it appropriately. If you have multiple scopes that use the same DG, you won't be able to tell which one is which unless the DNS entries are unique. you might temporarily disable the IP range on the network which will set the is_enable column to 0 (false) ... which will make it easier to locate.