Recently I noticed the SoftLayer UI has changed and part of that change was the ability to specify a subnet on a VLAN when ordering a virtual guest.
Has this support been implemented in the REST API json payload when specifying primaryNetworkComponent and primaryBackendNetworkComponent parameters to create a virtual guest?
Yes, Currently It's possible to set the subnets, you should define "primarySubnet" inside of "networkVlan" property, here a Rest example:
Replace: $user, $apiKey and the values for: networkVlanId and primarySubnet >> id with your own information