In a test project, with an instance template, I was able to create 2 VM instances with consecutive internal IP addresses (under the same subnet).
I followed these steps:
1) On Cloud Console, went to “Instance templates” page
2) Selected an existing template (a new one can be created too)
3) Clicked on “Create VM”
4) Expanded the ‘Management, Security, Disks, Networking, Sole tenancy’ section and selected “Networking”
5) Edited the ‘Network interface’ section with the following:
- Under ‘Primary internal IP’, chose ‘Reserve a static internal IP address’ and then put a custom IP address (e.g. 10.128.0.2)
(For External IPs, there is no option to customize the reservation)
It is worth mentioning that Google Groups is a place for non-technical how-to questions (where you're likely to find information like service status updates and release notes, and ranging from book recommendations to creative shortcuts) [1].
If you need any help with this particular configuration with proxies, I would recommend you to consider reaching out to Stack Exchange sites [2] (e.g. Server Fault [3] or Stack Overflow [4]) where Google also participates that can help you find answers and troubleshoot problems.
(Please share the step by step instructions on what you have done so far omitting PII/sensitive information and more details about your end goal, so that the community can try to address your query accordingly)