The Documentation for using your own network in the DB Security Data Masking and Subsetting livelab has a potential issue (that I ran into), The Stack / terraform build assumes a private ip address that may not be in your preexisting VCN. (In my VCN the CIDR block I used was 192.168.3.0/24. The Terraform script tried to use a 10.x.x.x address and it failed. I would update the documentation to include the CIDR block that is needed as part of the pre-check - or drop the option to create using an existing VCN.