Azure-to-GCP Connectivity Explained

By Khimananda Oli | Last reviewed: August 2026

Establishing reliable network paths between Microsoft Azure and Google Cloud Platform remains a primary challenge for teams operating distributed systems. This Azure-to-GCP connectivity explained guide cuts through vendor marketing to focus on the three viable production patterns: site-to-site IPsec VPN, dedicated Partner Interconnect, and direct physical Cross-Cloud Interconnect. Whether you are migrating legacy workloads or building active-active deployments, choosing the wrong transport layer leads to latency spikes, unpredictable egress costs, and compliance failures during audits.

How Do You Choose the Right Azure-to-GCP Connectivity Model?

Selecting a connectivity model is an infrastructure decision that dictates your operational overhead, cost floor, and failure domains. In practice, I evaluate three criteria before touching any Terraform code: required bandwidth ceiling, acceptable latency jitter, and data residency constraints. For most Nepal-based fintechs or global SaaS platforms handling sensitive user data, the public internet is often non-negotiable due to regulatory pressure.

If your workload involves observability pipelines shipping terabytes of telemetry daily, IPsec VPN will saturate quickly and introduce packet loss that corrupts trace correlation. Conversely, provisioning a 10 Gbps Direct Interconnect for a simple database replication task burning 50 Mbps is financial negligence. Most production environments I architect in 2026 land on Partner Interconnect because it balances SLA guarantees with operational flexibility, avoiding the long lead times of physical cross-connects while keeping traffic off the public internet.

How Do You Configure Site-to-Site IPsec VPN Between Azure and GCP?

Site-to-site IPsec VPN remains the fastest path to functional connectivity. It requires no third-party vendors and can be provisioned entirely via Infrastructure as Code. However, a common mistake is treating this as "set and forget." Without proper tuning, MTU mismatches and rekeying intervals cause silent application timeouts that mimic database issues.

Step-by-Step VPN Configuration

1. Create the Azure Virtual Network Gateway: Use a VpnGw2 or higher SKU for production. Standard SKUs lack the throughput for sustained cross-cloud sync. Assign a static public IP.
2. Provision the GCP Cloud VPN Gateway: Deploy an HA VPN gateway in the target region. Select "Route-based" tunnel mode to simplify BGP integration later.
3. Configure IKEv2 Parameters: Both clouds must match exactly. Use AES-256-GCM for encryption, SHA-256 for integrity, and DH Group 14 (MODP 2048). Avoid DH Group 1 or 2; they are deprecated and flagged by security scanners.
4. Set Up BGP Sessions: Static routes are unmanageable at scale. Configure BGP ASN 65515 on Azure and a private ASN (e.g., 65001) on GCP. Advertise only specific CIDR blocks, never 0.0.0.0/0, to prevent accidental transit routing.
5. Tune TCP MSS Clamping: Set MSS to 1380 bytes on both sides. IPsec headers consume ~60 bytes; standard 1500 MTU causes fragmentation that drops large payloads like protobuf messages or compressed backups.

# Example Terraform snippet for GCP HA VPN Tunnel (IKEv2)
resource "google_compute_vpn_tunnel" "azure_primary" {
  name          = "azure-vpn-tunnel-1"
  region        = "asia-south1"
  vpn_gateway   = google_compute_ha_vpn_gateway.azure_gcp.id
  peer_gcp_gateway = null
  peer_external_gateway = google_compute_external_vpn_gateway.azure_ext.id
  router        = google_compute_router.azure_bgp.id
  shared_secret = var.ipsec_shared_secret
  
  # Critical: Match Azure IKEv2 proposal exactly
  ike_version   = 2
}

# BGP Peer configuration with explicit ASN
resource "google_compute_router_peer" "azure_peer" {
  name                      = "azure-bgp-peer"
  router                    = google_compute_router.azure_bgp.name
  region                    = "asia-south1"
  peer_ip_address           = azurerm_public_ip.vpn_gateway_ip.ip_address
  peer_asn                  = 65515
  advertised_route_priority = 100
}

After provisioning, validate tunnel status using gcloud compute vpn-tunnels describe and Azure's Connection Monitor. If tunnels flap every 4–6 hours, check your Phase 2 rekey lifetime; Azure defaults to 3600 seconds while GCP may differ. Align them to prevent renegotiation races.

When Should You Use Google Cloud Interconnect Instead of VPN?

VPN works until it doesn't. The moment you need consistent sub-10ms latency, guaranteed bandwidth, or SOC 2 Type II evidence of traffic isolation, you must graduate to Google Cloud Interconnect. Partner Interconnect uses authorized service providers like Equinix or Megaport to create virtual circuits between Azure ExpressRoute and GCP. You get private connectivity without managing physical ports.

The trade-off is complexity and cost. Partner Interconnect requires coordinating with the provider's portal, exchanging LOAs, and configuring BGP MD5 authentication. Expect 2–4 weeks for initial provisioning versus minutes for VPN. However, for teams running PostgreSQL replication across clouds, the deterministic latency prevents write skew and reduces replication lag from seconds to milliseconds.

What Are the Performance and Cost Trade-offs Between Azure-to-GCP Connectivity Options?

Understanding the quantitative differences prevents budget shocks. Egress pricing varies dramatically: VPN traffic incurs standard internet egress rates on both sides, while Interconnect uses discounted private egress tiers. Below is a comparison based on current 2026 pricing for the Asia-South (Mumbai) ↔ Southeast Asia (Singapore) corridor, a common route for Nepal-facing services leveraging regional redundancy.

Note the hidden cost in Direct Interconnect: the monthly port fee ($1,500–$3,000+) applies regardless of utilization. Unless you sustain >5 Gbps continuously, Partner Interconnect delivers better unit economics. Also factor in provider fees; Megaport and Equinix charge separately for the virtual circuit, which can add $300–$800/month depending on bandwidth tier.

How Do You Secure and Monitor Cross-Cloud Traffic for Compliance?

Connectivity without observability is a liability. Every byte crossing the Azure-GCP boundary must be logged, inspected, and auditable. I enforce three non-negotiable controls regardless of transport type.

• Mutual Authentication: For VPN, use certificate-based IKEv2 instead of pre-shared keys in production. Rotate certificates quarterly via automated pipelines. For Interconnect, enable BGP MD5 authentication and MACsec encryption where supported by the provider.
• Network Segmentation: Never connect entire VNets/VPCs directly. Use hub-spoke topologies with Azure Firewall or GCP Cloud NGFW as inspection points. Apply least-privilege routing: advertise only the specific subnets required for the workload, not the entire address space.
• Unified Observability: Export flow logs from both Azure NSG and GCP VPC Flow Logs to a centralized platform. Correlate connection IDs across clouds to trace requests end-to-end. Alert on tunnel state changes, BGP session resets, and anomalous bandwidth spikes that indicate exfiltration or misconfiguration.

For teams subject to ISO 27001 or SOC 2, document the encryption standards, key rotation procedures, and access controls governing the interconnect. Auditors will request evidence that traffic cannot be intercepted or modified in transit. Partner Interconnect providers typically supply annual SOC 2 Type II reports covering their fabric; attach these to your own compliance artifact repository. Automated evidence collection via CI-integrated compliance checks reduces audit preparation time from weeks to hours.

Next Steps for Production Azure-to-GCP Connectivity

Azure-to-GCP connectivity explained is ultimately about matching business requirements to technical constraints without over-engineering. Start with IPsec VPN for validation and non-production workloads. Graduate to Partner Interconnect when latency sensitivity, compliance mandates, or bandwidth costs justify the investment. Reserve Direct Interconnect for high-performance computing or regulated data center extensions where every millisecond matters. Whichever path you choose, treat the connection as a first-class infrastructure component: version-control its configuration, monitor its health relentlessly, and review its security posture quarterly. If your team needs help designing a compliant, cost-efficient multi-cloud network that passes audits and handles production traffic, reach out to discuss your architecture.