This page outlines common network peering connection issues and possible resolutions.
Most peering issues come from overlapping CIDR ranges, incomplete routing, missing access list entries, or the DNS resolving cluster hostnames to public instead of private IP addresses. Generally, if traffic doesn't flow over the peered connection, verify the network prerequisites, then test the DNS configuration and connectivity from inside the peered network. For multi-region deployments, verify the peering configuration for each region.
In addition, check the following:
Confirm that the Atlas CIDR and the peer VPC or VNet CIDR do not overlap and that both use RFC 1918 private address space.
Verify that the peering request is accepted on the cloud provider side and that Atlas shows the peering connection as available.
Check the cloud-side route tables and confirm that routes to the Atlas CIDR use the peering connection.
Make sure that the peer CIDR is added to the Atlas IP access list and that the cloud-side firewall or security group rules allow the required traffic.
Validate DNS resolution from a host inside the peered network and confirm that cluster hostnames resolve to private IP addresses.
Test connectivity from a VM or other workload inside the peered network instead of from a local machine outside the peered environment.
Some network topologies have additional limitations. Review the provider-specific peering requirements if you use custom DNS, on-premises connectivity, or cloud-specific services that impose routing or peering constraints.