If the gcp project does not have a vpc with that name "default" the packer build cannot be executed.
$ packer build template.json
bastion: output will be in this color.
client: output will be in this color.
server: output will be in this color.
==> bastion: Checking image does not exist...
==> client: Checking image does not exist...
==> server: Checking image does not exist...
==> client: Creating temporary rsa SSH key for instance...
==> bastion: Creating temporary rsa SSH key for instance...
==> server: Creating temporary rsa SSH key for instance...
==> client: Using image: ubuntu-1804-bionic-v20210108
==> client: Creating instance...
client: Loading zone: us-east1-b
client: Loading machine type: n1-standard-1
client: Requesting instance creation...
==> bastion: Using image: ubuntu-1804-bionic-v20210108
==> bastion: Creating instance...
bastion: Loading zone: us-east1-b
bastion: Loading machine type: n1-standard-1
==> server: Using image: ubuntu-1804-bionic-v20210108
==> server: Creating instance...
server: Loading zone: us-east1-b
server: Loading machine type: n1-standard-1
bastion: Requesting instance creation...
server: Requesting instance creation...
==> client: Error creating instance: googleapi: Error 400: Invalid value for field 'resource.networkInterfaces[0].network': 'global/networks/default'. The referenced network resource cannot be found., invalid
Build 'client' errored after 9 seconds 111 milliseconds: Error creating instance: googleapi: Error 400: Invalid value for field 'resource.networkInterfaces[0].network': 'global/networks/default'. The referenced network resource cannot be found., invalid
==> bastion: Error creating instance: googleapi: Error 400: Invalid value for field 'resource.networkInterfaces[0].network': 'global/networks/default'. The referenced network resource cannot be found., invalid
Build 'bastion' errored after 10 seconds 27 milliseconds: Error creating instance: googleapi: Error 400: Invalid value for field 'resource.networkInterfaces[0].network': 'global/networks/default'. The referenced network resource cannot be found., invalid
==> server: Error creating instance: googleapi: Error 400: Invalid value for field 'resource.networkInterfaces[0].network': 'global/networks/default'. The referenced network resource cannot be found., invalid
Build 'server' errored after 10 seconds 436 milliseconds: Error creating instance: googleapi: Error 400: Invalid value for field 'resource.networkInterfaces[0].network': 'global/networks/default'. The referenced network resource cannot be found., invalid
==> Wait completed after 10 seconds 436 milliseconds
==> Some builds didn't complete successfully and had errors:
--> client: Error creating instance: googleapi: Error 400: Invalid value for field 'resource.networkInterfaces[0].network': 'global/networks/default'. The referenced network resource cannot be found., invalid
--> bastion: Error creating instance: googleapi: Error 400: Invalid value for field 'resource.networkInterfaces[0].network': 'global/networks/default'. The referenced network resource cannot be found., invalid
--> server: Error creating instance: googleapi: Error 400: Invalid value for field 'resource.networkInterfaces[0].network': 'global/networks/default'. The referenced network resource cannot be found., invalid
==> Builds finished but no artifacts were created.
If the gcp project does not have a vpc with that name "default" the packer build cannot be executed.