A company configured an AWS Cloud WAN core network with edge locations in us-east-1 and us-west-1. Each edge has two segments: development and staging, both using the default core network policy. A development VPC (10.0.0.0/16) is attached to the development segment in us-east-1; a staging VPC (10.5.0.0/16) is attached to the staging segment in us-west-1. Both VPC route tables send 0.0.0.0/0 to the core network. The team cannot get the two VPCs to communicate through the Cloud WAN; security groups and NACLs are not blocking traffic. What must the team do to enable communication between these VPCs via the core network?

The core network policy defines routing within Cloud WAN. For VPCs attached to different segments to communicate, Cloud WAN needs explicit routes in its policy to direct traffic between those segments. Adding static routes in the core network policy for each segment, pointing to the respective VPC attachments, allows Cloud WAN to learn the routes and forward traffic between the development and staging VPCs. Updating VPC route tables with static routes for their own CIDRs is incorrect because the VPCs already send all non-local traffic (0.0.0.0/0) to the Cloud WAN, which is the correct initial step. Updating the segment filter is not a standard Cloud WAN routing mechanism for inter-segment communication. Setting isolate-attachments to False is not applicable here as the issue is about inter-segment routing, not intra-segment isolation.