# VPC Peering GCP Atlas > Source-anchored research for VPC Peering GCP Atlas. Run status: COMPLETED. Parent: [Global AI Hub Research Corpus](https://llms-explorer.com/tree/global-ai-hub-research-corpus/) · 5 facets · 19 facts · page: https://llms-explorer.com/tree/vpc-peering-gcp-atlas/ ## How it works - For a Google Cloud application VPC and Atlas GCP network, Atlas specifies one peering connection because Google Cloud VPCs are global; do not apply the AWS/Azure per-region peering rule to GCP. (medium confidence) — [source](https://www.mongodb.com/docs/atlas/manage-vpc-peering.md) - In the January–February 2024 LDAP discussion, the customer reported that Atlas support confirmed their Atlas GCP cluster could not reach an LDAP server through Cloud VPN because Atlas did not accept the required custom routes. This is a reported configuration outcome, not an independent reproduction. (medium confidence) — [source](https://www.mongodb.com/community/forums/t/gcp-peering-to-access-private-ldap/263762) - Plan non-overlapping address ranges before peering: Atlas requires its CIDR not to overlap the application VPC, and Google rejects peering when subnet ranges overlap. (medium confidence) — [source](https://www.mongodb.com/docs/atlas/security-vpc-peering.md) ## How-to and procedures - Configure peering in Atlas using the customer GCP project ID and VPC name, then configure the reciprocal Google Cloud connection using the Atlas GCP project ID and Atlas VPC name. These are distinct from the Atlas application project identifier. (high confidence) — [source](https://www.mongodb.com/docs/atlas/manage-vpc-peering.md) ## Problems, failure modes and limitations - Atlas documents that it does not accept custom routes for GCP peering. Consequently, routes-based GKE clusters and clients reached through Cloud VPN or Interconnect cannot use this Atlas peering path as documented. (medium confidence) (verified as of 2026-10-14) — [source](https://www.mongodb.com/docs/atlas/manage-vpc-peering.md) - Google Cloud peering is non-transitive: peering A with B and A with C does not connect B to C. Generic Google Cloud peering can exchange custom static and dynamic routes, so Atlas’s refusal to import custom routes is an additional product limitation. (medium confidence) — [source](https://cloud.google.com/vpc/docs/vpc-peering) - Google VPC peering does not provide transitive routing. A second application VPC cannot inherit Atlas reachability merely by peering with the application VPC that peers with Atlas. (low confidence) — [source](https://cloud.google.com/vpc/docs/vpc-peering) ## Comparisons and alternatives - A 2021 GKE-to-Atlas question records failed ping tests and an inactive-link diagnostic suggestion. It does not establish a confirmed root cause; use it as a troubleshooting lead rather than proof of a routing bug. (low confidence) — [source](https://stackoverflow.com/questions/69864794/mongodb-atlas-vpc-peering-network-not-connecting-to-gcp-vpc) ## Facts and statements - GCP clients must use the Atlas Private IP for Peering connection string and place the relevant source CIDR on the Atlas IP access list; creating peering alone is insufficient. (high confidence) — [source](https://www.mongodb.com/docs/atlas/manage-vpc-peering.md) - Plan non-overlapping network ranges before creating peering. Google Cloud rejects overlapping subnet ranges across peered VPCs; Atlas GCP CIDR selection also constrains the address space available for its regional deployments. (high confidence) — [source](https://www.mongodb.com/docs/atlas/manage-vpc-peering.md) - Terraform issue #917 reports GCP peering stuck Pending/Inactive with an Atlas network_name of default while the Google-side configuration referenced a different VPC resource. Verify that both sides identify the intended customer network before attributing a pending link to a provider defect. (medium confidence) — [source](https://github.com/mongodb/terraform-provider-mongodbatlas/issues/917) - The Atlas CLI exposes atlas networking peering create gcp and atlas networking peering watch . The create command can create an Atlas VPC if one does not exist; the customer must still configure the Google Cloud side. (high confidence) — [source](https://www.mongodb.com/docs/atlas/cli/current/command/atlas-networking-peering-create-gcp.md) - Google documents Direct VPC egress for Cloud Run without a Serverless VPC Access connector. This scopes Atlas’s connector-only wording, but the reviewed Google page alone does not verify end-to-end Atlas peering compatibility. (medium confidence) (verified as of 2026-10-26) — [source](https://docs.cloud.google.com/run/docs/configuring/vpc-direct-vpc) - Atlas peering connects an application VPC privately to a dedicated Atlas deployment. Free and Flex clusters do not support peering in the cached Atlas documentation captured on 2026-10-14. (medium confidence) (verified as of 2026-10-14) — [source](https://www.mongodb.com/docs/atlas/manage-vpc-peering.md) - A firsthand GKE incident reported private-hostname connection timeouts while the standard connection worked; the reporter resolved it by allowing the pod address range in Atlas on 2020-08-17. This supports checking the actual client source range during troubleshooting, without establishing a universal GKE fix. (medium confidence) — [source](https://serverfault.com/questions/1030378/error-at-connecting-to-mongodb-atlas-via-vpc-peering-from-gcp-kubernetes-cluster) - Google VPC peering does not exchange firewall rules or policies; each VPC keeps its own controls. (low confidence) — [source](https://cloud.google.com/vpc/docs/vpc-peering) - Atlas documentation captured on 2026-10-14 says its GCP peering does not accept custom routes, preventing routes-based GKE and client access through Cloud VPN or Interconnect; it identifies VPC-native GKE as supported. This is an Atlas constraint, not a general inability of Google peering to exchange custom routes. (medium confidence) (verified as of 2026-10-14) — [source](https://www.mongodb.com/docs/atlas/manage-vpc-peering.md) - Atlas documents an API option for smaller GCP network containers, /21 through /24, with a /24 allocation per selected region; the UI requires /18 or larger. Restricted regions constrain future cluster placement, so address sizing must include growth plans. (low confidence) (verified as of 2026-10-14) — [source](https://www.mongodb.com/docs/atlas/manage-vpc-peering.md) - The Atlas CLI exposes atlas networking peering create gcp with --gcpProjectId, --network and --atlasCidrBlock; the setup guide separately requires the Google-side connection and offers peering watch for readiness. (medium confidence) (verified as of 2026-10-14) — [source](https://www.mongodb.com/docs/atlas/cli/current/command/atlas-networking-peering-create-gcp.md)