AWS Cloud WAN Routing Policy: Fine-Grained Control for Global Networks

AWS did not make Cloud WAN interesting by adding another dashboard. It made Cloud WAN interesting by letting you control the routes themselves. On November 20, 2025, AWS launched Cloud WAN Routing Policy, and that turned the core network policy from “define the shape of the network” into “define how traffic should actually move.”

That sounds subtle. It is not. If you have ever tried to keep a global AWS network clean after the fifth region, the problem is usually not connectivity. It is route sprawl, asymmetry, and the constant question of which attachment should learn which prefix. Routing Policy gives you a way to answer that in the policy layer instead of patching route tables by hand.

What Routing Policy Adds

Cloud WAN already lets you define segments and attachments in one place. Routing Policy adds the part that network teams usually end up building with manual filters and static route workarounds:

• route filtering, so you can allow or drop specific routes
• route summarization, so you do not leak every internal prefix everywhere
• path preference controls, including BGP attributes like local preference, AS_PATH, and MED
• BGP community support, so route intent can survive between attachments and regions

AWS says Routing Policy is supported on all Cloud WAN attachment types, including VPC, VPN, Connect, Direct Connect, and peering attachments. That matters. It means the policy model can govern both the AWS side of the house and the external edge where most of the mistakes happen.

There is also a hard version detail that is easy to miss: you need core network policy version 2025.11 to use Routing Policy and BGP community support.

Why It Matters

The real value is not “more knobs.” It is fewer side effects. A global network with dozens of VPCs and on-prem sites usually fails because every new attachment expands the blast radius of routing mistakes. One bad summary can leak a prefix into the wrong segment. One missing filter can create a path nobody intended. One asymmetrical path can make a firewall look broken when the route policy is the actual problem.

Cloud WAN Routing Policy gives you a central place to express what is allowed, what is summarized, and which path should win when multiple links exist. That is exactly the kind of control you want once Transit Gateway hub-and-spoke networking stops being enough on its own.

The payoff is biggest when Cloud WAN is already the global control plane and you are stitching in AWS Interconnect for private multicloud or partner-based last-mile connectivity. In that setup, Cloud WAN is the policy engine, Interconnect is the transport, and your VPC design still lives in the normal AWS networking layer.

The Quotas You Actually Care About

The quotas tell you how far you can push the feature before the design starts to bend:

• 10 routes per core network across all segments
• 10 rules per routing policy
• 5 match conditions per rule
• 5 routing policies per association type
• 8,500 byte MTU for VPC traffic over the core network

That is enough for sane architectures. It is not enough for people who try to stuff every exception into one giant policy document and call it centralized control.

The Gotchas

The first gotcha is that Routing Policy does not replace network design. It sits on top of it. If your segments are messy or your CIDR plan overlaps, Routing Policy will just make the mess more consistent.

The second gotcha is that the policy model is opinionated about control, but not about ignorance. You still need to understand BGP, route summarization, and how asymmetry shows up in real traffic. Cloud WAN can enforce intent. It cannot make a bad routing hypothesis true.

The third gotcha is operational. Policy versions are not the same thing as live policy. You create a version, review it, and then deploy it. That is good. It is also one more place where teams can confuse “I changed it” with “it is live.”

The fourth gotcha is that Cloud WAN and Transit Gateway solve different problems. Transit Gateway is the regional hub. Cloud WAN is the global policy and segmentation layer. If you try to use one as a cheap substitute for the other, you will pay for it later in route churn.

When To Use It

Cloud WAN Routing Policy is for the point where the network team spends more time explaining route exceptions than shipping changes. If that sounds familiar, you are past the stage where per-VPC tweaking is the right answer.

For a small or stable topology, I would still stay with a normal VPC layout or a regional Transit Gateway setup. They are easier to read, easier to troubleshoot, and easier to hand to the next person on call.

The useful mental model is simple. Cloud WAN sets the routing intent, Transit Gateway handles the regional hub, and AWS Interconnect or Direct Connect moves the traffic. Keep those jobs separate and the whole thing stays less fragile.