[t3rabytes]

Pretty standard? Taking AWS for example:

- You can do this, but it's highly discouraged since it means no VPC peering if you ever need that.

- Can't do this at all with network interfaces, it all is via VPC peering.

- Can't change the VPC after an instance has been created, you have to take a snapshot and relaunch it.

[KingOfCoders]

I basically have no clue.

I thought one would have a node two VPC, e.g. app and database, so it can speak to both, but the load balancers can't.

With peering one would have an app VPC and a database VPC and peer them?

[vorpalhex]

In AWS you use a mix of private and public subnets within a single VPC.

Not sure best practice for DO since I haven't tried their VPC setup but it doesn't appear to have a way to let two VPCs interact yet.

[nerdbaggy]

Interesting, didn’t know that about AWS. In more familiar with the Google cloud version of VPC. Seems the DO implementation is more like the AWS version

[troutwine]

For what it's worth VPC ranges are allowed to overlap in GCP -- and do by default -- but then you aren't able to peer them. I kind of prefer the DO/AWS constraint.

[cbetti]

Agreed, having paid the cost of a few VPC moves to separate ranges on AWS in order to gain peering.

[Legogris]

No such constraint in AWS.

[troutwine]

I misremembered. Thanks for the clarification.

[t3rabytes]

Heh, no worries -- mostly the same deal there:

- You can do it, but it's probably not a great idea if you need to do VPC peering (or attach multiple VPCs to one VM, see next).

- Does actually work, but it does not work if the VPCs you're trying to attach to a single VM have overlapping CIDRs.

- Same deal, almost. You cannot add or remove network interfaces from an existing VM.

[rantwasp]

you cannot peer 2 vpcs that have an overlap but you can have multiple vpcs that have overlaps. it only matters for the 2 vpcs you want to peer

[vorpalhex]

But AWS tells you to not overlap them, and likely keeps that behavior for legacy reasons.

[moduspol]

I could have missed it, but I've never seen a suggestion not to overlap network addresses unless you want to peer them.

If you're launching ephemeral networks for testing VMs / virtual appliances in their own, isolated networks, it can be totally feasible to have lots of them using the same addresses. You can only create 5 VPCs (at all) by default per AWS account, but they'll raise that limit for you if you request it.