Migrate from legacy network in GCE

Question

Long story short - I need to use networking between projects to have separate billing for them.

I'd like to reach all the VMs in different projects from a single point that I will use for provisioning systems (let's call it coordinator node).

It looks like VPC network peering is a perfect solution to this. But unfortunately one of the existing networks is "legacy". Here's what google docs state about legacy networks.

About legacy networks Note: Legacy networks are not recommended. Many newer GCP features are not supported in legacy networks.

OK, naturally the question arises: how do you migrate out of legacy network? Documentation does not address this topic. Is it not possible?

I have a bunch of VMs, and I'd be able to shutdown them one by one:

1. shutdown
2. change something
3. restart

unfortunately it does not seem possible to change network even when VM is down?

EDIT: it has been suggested to recreate VMs keeping the same disks. I would still need a way to bridge legacy network with new VPC network to make migration fluent. Any thoughts on how to do that using GCE toolset?

Answer 1

One possible solution - for each VM in the legacy network:

1. Get VM parameters (API get method)
2. Delete VM without deleting PD (persistent disk)
3. Create VM in the new VPC network using parameters from step 1 (and existing persistent disk)

This way stop-change-start is not so different from delete-recreate-with-changes. It's possible to write a script to fully automate this (migration of a whole network). I wouldn't be surprised if someone already did that.

UDPATE

https://github.com/googleinterns/vm-network-migration tool automates the above process, plus it supports migration of a whole Instance Group or Load Balancer, etc. Check it out.