Treat the two environments as separate routed networks, then build a site-to-site VPN with static addressing, route propagation, and matching firewall or security group rules on both sides. Use non-overlapping CIDR ranges so traffic can be routed cleanly. The operational goal is predictable network reachability, not just encrypted transport. That keeps access controllable and easier to troubleshoot.
Why the network model matters more than the transport cipher
Cross-cloud workload connectivity works best when teams stop treating every connection as a one-off exception. A routed network model gives each cloud a clear address space, a known path, and an enforceable boundary. That makes the link between AWS and Google Cloud easier to reason about, easier to audit, and less brittle than ad hoc peering or direct allow-listing.
The practical difference is that routing becomes the control point. You can define which subnets may talk, which ports are open, and which side is allowed to initiate traffic, instead of spreading that logic across many bespoke firewall entries and application-specific exceptions.
For workload-to-workload communication, the architectural win is predictability. When the network plan is deliberate, teams can separate connectivity from application logic, which reduces surprise dependencies and makes future changes, failover, and incident review far easier.
How to design AWS and Google Cloud connectivity cleanly
The simplest durable pattern is a site-to-site VPN between the two environments, with static addressing and non-overlapping CIDR ranges so routes do not collide. Route propagation should be configured deliberately, not assumed, and both sides should enforce matching security group or firewall rules so permitted paths are symmetrical and understandable.
This design is stronger than “just make it reachable” because it preserves routing intent. If the destination subnet, source subnet, and next hop are all explicit, teams can troubleshoot with packet flow logic instead of guessing which implicit policy blocked the connection.
That approach also scales better when workloads move, are replaced, or expand into new subnets. The connectivity model stays stable while the workloads change underneath it, which is exactly what you want in multi-cloud operations.
What goes wrong with point-to-point access
Ad hoc connectivity usually fails because it creates hidden trust paths. Each new exception increases the chance of asymmetric rules, stale routes, overlapping address ranges, or an unnoticed path that bypasses the intended control plane.
It also increases operational ambiguity. When traffic depends on scattered exceptions, teams lose confidence about whether a request failed because of routing, DNS, firewall policy, or application behavior. That slows recovery and encourages more exceptions, which compounds the problem.
SPIFFE workload identity concepts are useful when the network path is only one part of the trust model, because they separate workload identity from network reachability and reduce dependence on brittle source IP assumptions.
Risk and Threat Considerations
Ad hoc cross-cloud connectivity creates exposure because every extra exception expands the reachable surface. Misaligned routing, broad firewall rules, or overlapping CIDR ranges can open unintended paths, make segmentation ineffective, and obscure where trust is actually being granted.
Failure mechanism: A team adds temporary connectivity to unblock a deployment, but the route and rule set never get normalized. Over time, that leaves stale pathways, broad network access, and hard-to-review exceptions that are difficult to detect in routine operations.
Impact: A compromise in one workload can move farther than intended, troubleshooting becomes slower, and the environment becomes more fragile because administrators no longer have a single authoritative view of permitted reachability.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
NIST SP 800-53 Rev 5, CIS Controls v8 and CSA Cloud Controls Matrix set the technical controls, while ISO/IEC 27001:2022 defines the regulatory obligations.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST SP 800-53 Rev 5 | SC-7 — Boundary Protection | Cross-cloud routing and firewall boundaries are central to controlled workload connectivity. |
| AC-4 — Information Flow Enforcement | Route and rule design determines which workloads may exchange traffic across clouds. | |
| Recommendation — Define and enforce boundary protections for AWS-to-Google Cloud traffic flows. Enforce explicit information-flow rules for permitted cross-cloud communications. | ||
| ISO/IEC 27001:2022 | A.8.20 — Network security | The question is fundamentally about securing and segmenting network connectivity between cloud environments. |
| Recommendation — Apply network security controls to segment, route, and restrict cross-cloud access. | ||
| CIS Controls v8 | CIS-12 — Network Infrastructure Management | The answer depends on managing routes, firewalls, and network segmentation across environments. |
| Recommendation — Document and manage network paths, firewall policy, and segmentation consistently. | ||
| CSA Cloud Controls Matrix | IAM — Identity and Access Management | Cloud network reachability is governed through cloud access policy and trust boundaries. |
| Recommendation — Align cloud access policy with least-privilege connectivity between environments. | ||
Practitioner Guidance
What to prioritise: Define the network boundary first, then decide what traffic is actually required between AWS and Google Cloud. If the workloads need only a small set of ports or subnets, keep the route and firewall scope narrow and explicit.
What to verify: Confirm that the CIDR ranges never overlap, that routes are symmetric enough for the traffic pattern you expect, and that both clouds enforce the same allow-list intent. If a path is hard to explain in one sentence, it is probably too implicit.
What good looks like: Teams can point to one documented connectivity pattern, one set of route rules, and one small policy surface for each workload relationship. The result is not just encrypted transport, but controlled, debuggable reachability.
Practitioner takeaway: In multi-cloud, the safest network design is usually the one that is easiest to reason about under failure, because clarity in routing and policy matters more than adding another ad hoc exception.
Related resources from NHI Mgmt Group
- How should security teams govern multi-cloud IAM across AWS, Azure, and Google Cloud without creating policy drift?
- How should security teams investigate non-human access across cloud and SaaS environments without relying on complex graph query skills?
- How should security teams manage cloud posture across AWS, Azure, Google Cloud, Kubernetes, and Microsoft 365 without creating operational gaps?
- How should security teams manage employee access across cloud resources without relying on disconnected admin tools?
Deepen Your Knowledge
Reviewed and updated by the NHIMG editorial team on September 27, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org
