If you're on a private network (like your own DC), I'd argue that network-based security is a poor idea because then an attacker just needs to plug in and have pretty easy access.

If you're on the public cloud, I'd argue that this is an even bigger problem as you're then relying on VPC (or the equivalent) to always work correctly.

Why not ignore the networking and just build in robust security? Pubkey authentication where possible, random long passwords where not? Retry limits for clients, network intrusion detection, etc. To me, relying on the network to keep you secure seems a bit like a crutch.