Change effective on 12 September 2018
When creating a Private Space using the Heroku CLI, you can now provide the CIDR ranges to be used for the dyno and data VPCs associated with the Private Space:
$ heroku spaces:create --cidr 172.16.0.0/16 --data-cidr 172.17.0.0/20 --space my-space
The CIDR ranges have to be from RFC 1918 blocks. The dyno VPC (
cidr) has to be a
/16 block. The data VPC (
data-cidr) has to be at least a
See the Private Space Dev Center article for details.