How to Build Secure Connectivity Between Multiple Cloud Providers
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A practical technical guide covering IPsec VPN, private interconnects, AWS Transit Gateway, Azure Virtual WAN, GCP NCC, SD-WAN overlay, Zero Trust, BGP design, and encryption in transit for AWS, Azure, and GCP multi-cloud deployments in 2025
By Route XP | Published: March 2026 | Updated: March 2026 | Multi-Cloud, Network Security, Cloud Networking
Multi-Cloud Secure Connectivity — Connecting AWS, Azure, and GCP with IPsec, Private Interconnects, and SD-WAN
- The Multi-Cloud Reality and Its Networking Challenges
- Three Connectivity Models: VPN, Private Interconnect, SD-WAN
- IPsec VPN Between Cloud Providers: Architecture and Limits
- Private Interconnects: AWS Direct Connect, Azure ExpressRoute, GCP Cloud Interconnect
- Cloud-Native Transit Hubs: TGW, vWAN, and NCC
- SD-WAN Overlay for Multi-Cloud: The Unified Fabric
- BGP Design for Multi-Cloud Routing
- Encryption in Transit: What Gets Encrypted and What Doesn't
- Zero Trust for Multi-Cloud: Beyond the Network Perimeter
- Reference Architecture Patterns
- Vendor and Tool Selection Guide
- Frequently Asked Questions
1. The Multi-Cloud Reality and Its Networking Challenges
Multi-cloud is no longer a strategic aspiration — it is the operational reality for most enterprises. Workloads are distributed across AWS, Azure, and GCP for reasons ranging from contractual vendor diversification and regulatory data-residency requirements to engineering pragmatism: some services are simply best-in-class on one provider (Azure Active Directory, AWS SageMaker, GCP BigQuery) and organizations want to use each cloud for what it does best.
The networking challenge this creates is profound. Each cloud provider operates its own private backbone, its own IP addressing model, its own routing protocols, and its own security constructs. Connecting workloads across these boundaries securely, reliably, and at acceptable latency is fundamentally a network engineering problem — and one that has no single perfect answer. The wrong architectural choice leads to security gaps, performance bottlenecks, spiraling data egress costs, or operational complexity that makes the environment impossible to maintain at scale.
This guide provides a rigorous technical framework for solving the multi-cloud connectivity problem: from basic IPsec VPN tunnels to private interconnects, cloud-native transit hubs, SD-WAN overlays, BGP routing design, encryption-in-transit coverage, and Zero Trust access models.
2. Three Connectivity Models: VPN, Private Interconnect, SD-WAN
Every multi-cloud networking architecture is built from some combination of three fundamental connectivity models. Understanding the trade-offs between them is the starting point for any design decision.
| Model | How It Works | Bandwidth | Latency | Cost | Best For |
|---|---|---|---|---|---|
| IPsec VPN | Encrypted tunnels over the public internet between cloud VPN gateways | 1–10 Gbps (gateway-limited) | Variable (internet-dependent) | Low — gateway + egress fees | Dev/test, lower-bandwidth, quick-start, budget-constrained |
| Private Interconnect | Dedicated Layer 2/Layer 3 circuits from colocation provider directly into cloud backbone | 1–100 Gbps per port | Consistent, low (bypasses internet) | High — port + circuit fees | Production, high-throughput, latency-sensitive, regulated data |
| SD-WAN Overlay | Software-defined overlay connecting cloud, on-prem, and branch via SD-WAN nodes deployed in each cloud region | Aggregates multiple underlays; 10–100+ Gbps | Optimized — path-aware steering | Medium — SD-WAN licences + VM costs | Full enterprise network unification; on-prem + multi-cloud + branch |
3. IPsec VPN Between Cloud Providers: Architecture and Limits
IPsec VPN is the lowest-barrier entry point for multi-cloud connectivity. All three major cloud providers offer managed VPN gateway services that terminate IPsec tunnels from external peers. The tunnel endpoints are public IPs assigned to the cloud VPN gateway — meaning traffic transits the internet between clouds, but is encrypted end-to-end.
Cloud VPN Gateway Capabilities (2025)
| Attribute | AWS VPN (Virtual Private Gateway / TGW) | Azure VPN Gateway | GCP Cloud VPN (HA VPN) |
|---|---|---|---|
| Max throughput per tunnel | 1.25 Gbps per tunnel | Up to 10 Gbps (VpnGw5AZ) | 3 Gbps per tunnel |
| ECMP / tunnel aggregation | Up to 4 tunnels via ECMP on TGW (5 Gbps aggregate) | Active-Active with 2 tunnels (dual-redundant) | HA VPN: 2 interfaces × 4 tunnels each = up to 24 Gbps aggregate |
| IKE versions supported | IKEv1, IKEv2 | IKEv1, IKEv2 | IKEv1, IKEv2 |
| BGP support | ✅ BGP over IPsec (dynamic routing) | ✅ BGP over IPsec (dynamic routing) | ✅ BGP over IPsec (dynamic routing) |
| Encryption | AES-128/256, SHA-1/256, DH 2/14/19/20/21/24 | AES-128/256 GCM, SHA-256/384, DH 2/14/24/ECP256/384 | AES-128/256 GCM, SHA-256, DH 1/2/5/14/15/16 |
| HA / redundancy | 2 public IPs per VGW; TGW for multi-AZ | Active-Active with zone-redundant SKU | HA VPN: 99.99% SLA with 2 interfaces |
AWS-to-Azure IPsec VPN: Configuration Pattern
aws ec2 create-customer-gateway \
--type ipsec.1 \
--public-ip 52.x.x.x \ # Azure VPN GW public IP
--bgp-asn 65515 # Azure BGP ASN
aws ec2 create-vpn-connection \
--transit-gateway-id tgw-0abc123 \
--customer-gateway-id cgw-0def456 \
--type ipsec.1 \
--options TunnelOptions='[{"TunnelInsideCidr":"169.254.21.0/30","Phase1EncryptionAlgorithms":[{"Value":"AES256"}]}]'
# IKEv2 recommended — set in tunnel options
# Always use DH Group 14+ (Group 2 is deprecated)
# Enable BGP for dynamic route exchange between clouds
4. Private Interconnects: AWS Direct Connect, Azure ExpressRoute, GCP Cloud Interconnect
Private interconnects bypass the public internet entirely. A physical circuit is provisioned from a colocation facility (Equinix, Digital Realty, Megaport) directly to the cloud provider's edge router. Traffic between your network and the cloud travels on this dedicated Layer 2/Layer 3 circuit — never touching the public internet. For multi-cloud architectures, the key insight is that major colocation providers peer with all three major cloud providers in the same facilities, making it possible to build private, any-to-any cloud connectivity through a common exchange point.
Private Interconnect Services — Technical Comparison
| Attribute | AWS Direct Connect | Azure ExpressRoute | GCP Cloud Interconnect |
|---|---|---|---|
| Port speeds | 1G, 10G, 100G dedicated; 50M–10G hosted | 50M–10G (Standard); up to 100G (Global Reach) | 10G, 100G (Dedicated); 50M–50G (Partner) |
| Routing model | BGP over private VIF or transit VIF; VRF-based separation | BGP with Microsoft Peering and Private Peering; ASN 12076 | BGP; requires Cloud Router in each VPC |
| Cloud-to-cloud via same colo | ✅ Via Direct Connect + partner cross-connect | ✅ Via ExpressRoute + partner cross-connect | ✅ Via Cloud Interconnect + partner cross-connect |
| Native encryption | ❌ Not encrypted by default — use MACsec or IPsec over DX | ⚠️ MACsec on ExpressRoute Direct only (10G/100G) | ❌ Not encrypted — use MACsec or IPsec overlay |
| SLA / availability | 99.9% (single); 99.99% (dual redundant) | 99.95% (Standard); 99.99% (Premium dual) | 99.9% (single VLAN); 99.99% (redundant) |
| Global reach / inter-region | SiteLink — connects Direct Connect locations globally over AWS backbone | ExpressRoute Global Reach — connects two ER circuits via Microsoft backbone | Cross-Cloud Interconnect — direct connection from GCP to AWS/Azure (limited locations) |
The Colocation Exchange Model for Multi-Cloud
The most operationally efficient private multi-cloud topology is built through a colocation exchange. Organizations deploy their own network equipment (routers or SD-WAN nodes) in a colocation facility that hosts all three major cloud providers. Each cloud connection terminates on the customer's equipment as a private circuit. Traffic between clouds travels: Cloud A → private circuit → customer router at colo → private circuit → Cloud B. The internet is never involved. Providers like Equinix Fabric, Megaport, and Console Connect offer software-defined cross-connects between cloud providers within their facilities — eliminating the need for physical router infrastructure entirely in some cases.
5. Cloud-Native Transit Hubs: TGW, vWAN, and NCC
All three major cloud providers offer managed transit hub services that simplify large-scale connectivity within their own cloud — and increasingly, across cloud boundaries. These are not multi-cloud solutions by themselves, but they are the anchor points of a multi-cloud architecture.
AWS Transit Gateway (TGW)
AWS Transit Gateway is a managed regional hub that connects VPCs, VPN connections, and Direct Connect gateways. Key capabilities for multi-cloud:
- VPN attachment: TGW supports up to 5,000 VPN connections, each with 2 tunnels and up to 1.25 Gbps per tunnel. ECMP across tunnels allows aggregated bandwidth up to 5 Gbps toward a single peer cloud
- Direct Connect Gateway attachment: A single Direct Connect Gateway can connect to TGW across regions, providing a global hub for on-premises and cloud-to-cloud traffic via AWS infrastructure
- TGW Peering: Connect TGW across AWS regions for inter-region cloud connectivity using AWS backbone — lower latency than internet VPN and no egress charges within AWS
- Route tables: TGW supports multiple route tables enabling complex traffic segmentation — VPCs in different security zones can be isolated from each other while still reaching the multi-cloud connection
Azure Virtual WAN (vWAN)
Azure Virtual WAN is Microsoft's managed global WAN service — a network of globally distributed Microsoft-managed hubs that connect Azure VNets, on-premises sites via VPN or ExpressRoute, and third-party SD-WAN appliances. For multi-cloud:
- Any-to-any connectivity: vWAN Standard tier enables branch-to-branch, VNet-to-VNet, and branch-to-VNet traffic to flow through Microsoft-managed hubs — all interconnected via Microsoft's private backbone
- Third-party NVA integration: vWAN supports deploying Network Virtual Appliances (Cisco Catalyst 8000v, Fortinet, Palo Alto) directly in the hub — enabling consistent security policy inspection on all traffic including traffic from AWS or GCP VPN peers
- ExpressRoute transit: A single vWAN hub can act as a transit point between multiple ExpressRoute circuits — enabling indirect connectivity between locations connected to different ER circuits
GCP Network Connectivity Center (NCC)
GCP Network Connectivity Center provides a hub-and-spoke model for connecting on-premises sites and other clouds to GCP VPCs. Spoke types include Cloud VPN, Cloud Interconnect, and Router Appliance (third-party VMs in GCP that act as BGP speakers). The Router Appliance spoke is particularly powerful for multi-cloud: deploy an SD-WAN or VPN appliance (Cisco CSR, Palo Alto, Aviatrix) as a GCP VM, and it becomes a transit point connecting GCP to AWS or Azure without traversing the internet.
| Feature | AWS Transit Gateway | Azure Virtual WAN | GCP Network Connectivity Center |
|---|---|---|---|
| External VPN peers | ✅ Up to 5,000 VPN connections | ✅ Up to 1,000 branches per hub | Via Cloud VPN spokes |
| 3rd-party NVA in hub | No native NVA — use inspection VPC pattern | ✅ Native NVA in vWAN hub (Cisco, Fortinet, Palo Alto) | ✅ Router Appliance spoke (SD-WAN VM) |
| Multi-region transit | ✅ TGW Peering across regions | ✅ Global mesh — all hubs interconnected | Via GCP global routing (VPC is global) |
| Route segmentation | ✅ Multiple route tables — flexible isolation | Routing intent policies (Basic/Custom) | VPC firewall rules + Cloud Router policies |
6. SD-WAN Overlay for Multi-Cloud: The Unified Fabric
SD-WAN is the most operationally powerful approach to multi-cloud networking because it provides a single unified overlay fabric that abstracts the underlying connectivity (internet VPN, private interconnect, MPLS) and applies consistent routing policy, security policy, and QoS across all sites and clouds simultaneously — from a single management plane.
The architecture is straightforward: deploy SD-WAN virtual appliances (vEdge or cEdge) as instances in each cloud region (AWS EC2, Azure VM, GCP Compute Engine). These cloud instances join the SD-WAN overlay as regular SD-WAN sites, establishing encrypted tunnels (IPsec or DTLS) back to the SD-WAN controllers and to all other SD-WAN sites — including on-premises data centers, branch offices, and the other cloud instances.
Cisco Catalyst SD-WAN (Viptela) Multi-Cloud Topology
On-Prem DC cEdge-DC
Branch-London cEdge-BR-LON
AWS us-east-1 cEdge-AWS-USE1 (EC2 c5.xlarge, 2 vNICs)
Azure West Europe cEdge-AZR-WEU (Azure D4s_v3, 2 NICs)
GCP europe-west1 cEdge-GCP-EW1 (n2-standard-4, 2 NICs)
All sites form IPsec/DTLS tunnels via SD-WAN overlay
vManage → vSmart → vBond control plane (hosted or cloud-managed)
OMP (Overlay Management Protocol) distributes routes between all sites
Centralized data policy steers traffic based on app, SLA, and path quality
Key SD-WAN Multi-Cloud Capabilities
| Capability | How It Solves the Multi-Cloud Problem |
|---|---|
| Application-aware routing | Steers traffic to AWS vs Azure vs on-prem based on app identity, real-time path quality (latency/jitter/loss), and business intent — not just static routing |
| Transport independence | Same policy applies whether the underlay is MPLS, internet VPN, Direct Connect, or ExpressRoute — the overlay abstracts transport type completely |
| Centralized encryption policy | IKEv2/IPsec or DTLS encryption on every tunnel — enforced from vManage, not configured per-device — ensuring all inter-cloud traffic is encrypted without manual per-tunnel configuration |
| Segmentation (VPN instances) | VRF-equivalent segmentation across the entire overlay — a finance segment in AWS cannot reach a dev segment in Azure unless explicit policy permits it, across all clouds simultaneously |
| Cloud OnRamp for IaaS | Cisco Cloud OnRamp (AWS, Azure, GCP) automates vEdge instance deployment, VPC/VNet integration, and route advertisement — reduces cloud SD-WAN node deployment from hours to minutes |
7. BGP Design for Multi-Cloud Routing
BGP is the universal routing protocol for multi-cloud connectivity. Every cloud provider's VPN gateway and private interconnect service runs BGP. Getting the BGP design right is critical — a misconfigured BGP topology can create routing loops, suboptimal paths, or accidental route leakage between clouds.
ASN Assignment Strategy
- Use private 4-byte ASNs for your transit routers: range 4200000000–4294967294 (RFC 6996). This avoids conflicts with public internet ASNs and the reserved 2-byte private range (64512–65534) which cloud providers often use internally
- AWS VGW/TGW: Default ASN 64512 (configurable 64512–65534 or 1–4294967295). Use a unique ASN per TGW to enable proper eBGP peering and prevent BGP loop prevention from blocking routes
- Azure: Microsoft uses ASN 12076 for ExpressRoute Microsoft Peering. Your ExpressRoute Private Peering uses your own ASN. Azure VPN Gateways use ASN 65515 by default (configurable)
- GCP: Cloud Router supports ASNs 16550 and 4200000000–4294967294 for peering. Each Cloud Router has a unique ASN
Route Advertisement Best Practices
# 1. Advertise specific prefixes only — never default route into a cloud
# Advertising 0.0.0.0/0 into a cloud VPC causes ALL traffic to route
# back through your on-premises — including internet-bound cloud traffic
# 2. Use BGP communities for route tagging
# AWS: community 7224:9300 (no export to Direct Connect peers)
# Azure: community 65517 (do not advertise to ExpressRoute peers)
# 3. Set MED (Multi-Exit Discriminator) for path preference
# Lower MED = preferred path
# Use MED to prefer private interconnect over VPN backup
# 4. Apply prefix-lists at cloud peering boundaries
# Filter inbound: reject cloud provider bogons and overly specific prefixes (/25 and longer)
# Filter outbound: advertise only your CIDR blocks — never re-advertise cloud prefixes to other clouds
# 5. Enable BFD on all cloud BGP sessions
# Faster failover than BGP hold-down timers alone
# AWS TGW: BFD supported on VPN connections (min 300ms)
# Azure ExpressRoute: BFD supported on Private Peering
8. Encryption in Transit: What Gets Encrypted and What Doesn't
One of the most misunderstood aspects of multi-cloud networking is the encryption coverage of different connectivity options. Engineers often assume that a "private" connection is also an "encrypted" connection. They are not the same thing.
| Connectivity Type | Internet Exposure | Layer 2/3 Encryption | How to Add Encryption |
|---|---|---|---|
| IPsec VPN (cloud-to-cloud) | Yes — internet transit | ✅ AES-256 IPsec — fully encrypted | Already encrypted — verify proposal uses AES-256-GCM + IKEv2 |
| AWS Direct Connect (private VIF) | No — private circuit | ❌ Not encrypted at circuit layer | Add IPsec over DX (VGW or TGW VPN on same VIF), or MACsec on 10G/100G Dedicated |
| Azure ExpressRoute (private) | No — private circuit | ❌ Not encrypted at circuit layer | MACsec on ExpressRoute Direct; or IPsec VPN over ER using Azure VPN GW |
| GCP Cloud Interconnect | No — private circuit | ❌ Not encrypted at circuit layer | HA VPN over Cloud Interconnect (IPsec tunnel inside the VLAN); or MACsec |
| SD-WAN overlay (any underlay) | Depends on underlay | ✅ IPsec/DTLS on every tunnel — enforced by controller | Already encrypted — no additional configuration needed |
| Within-cloud (intra-VPC/VNet) | No — provider backbone | ⚠️ Provider-dependent — AWS encrypts intra-region VPC traffic; Azure VNet generally not | Use TLS at the application layer (mTLS between services) — do not rely on network layer encryption within a cloud |
The defense-in-depth recommendation for regulated workloads: deploy three encryption layers — (1) MACsec or IPsec at the network layer for the interconnect circuit, (2) TLS 1.3 at the transport/application layer for all service-to-service communication, and (3) application-level encryption (customer-managed keys in a KMS) for data at rest. No single layer is trusted exclusively.
9. Zero Trust for Multi-Cloud: Beyond the Network Perimeter
A secure network connection between clouds is necessary but not sufficient. A workload in AWS that can reach a workload in Azure over an encrypted private circuit can still be exploited if the access control between them is based purely on IP addresses and network segments. Zero Trust principles extend security to the workload and identity layer — ensuring that even within a secure network tunnel, only authorized services can communicate.
Zero Trust for Multi-Cloud: Four Control Points
- Workload identity (mTLS): Every service — regardless of its cloud location — carries a cryptographic identity issued by a trusted certificate authority (SPIFFE/SPIRE, HashiCorp Vault, AWS ACM PCA). Service-to-service communication uses mutual TLS, where both sides present and verify certificates. An API in AWS proves its identity to a database in Azure before any data is exchanged. Istio service mesh and Envoy proxy implement this transparently at the sidecar level
- Cloud-native IAM boundary: Use AWS IAM Roles, Azure Managed Identities, and GCP Service Accounts with least-privilege scopes. Cross-cloud API calls should use federated identity (OIDC tokens) rather than static API keys — enabling centralized revocation and audit
- Network micro-segmentation: Apply security groups, NSGs (Azure), and VPC Firewall Rules with explicit allow lists between cloud workloads. Default-deny between clouds — only permit traffic that is explicitly needed for the application to function. Document every cross-cloud flow in a connectivity matrix and validate it against actual firewall rules quarterly
- SASE for user access: Employees and contractors accessing workloads across multiple clouds should not use cloud-specific VPN clients or jump hosts. A SASE platform with ZTNA provides a single access plane — users authenticate once and receive application-level access to workloads in any cloud based on their identity and device posture, without network-level exposure
10. Reference Architecture Patterns
The following patterns represent the most common multi-cloud secure connectivity architectures used in production environments today, ordered from simplest to most sophisticated.
Pattern 1 — Hub-and-Spoke via On-Premises
All cloud connections (Direct Connect, ExpressRoute, Cloud Interconnect) terminate at the on-premises data center, which acts as the transit hub between clouds. Traffic between AWS and Azure travels: AWS VPC → Direct Connect → on-prem core router → ExpressRoute → Azure VNet. Simple to operate for organizations with a strong on-premises footprint, but introduces on-premises as a latency and bandwidth bottleneck for cloud-to-cloud traffic.
Pattern 2 — Colocation Exchange Hub
Customer router or SD-WAN device deployed in a colocation facility (Equinix, Digital Realty) with private circuits to each cloud provider. Cloud-to-cloud traffic flows through the colo device without traversing the on-premises data center. Eliminates the on-premises bottleneck while maintaining a dedicated hardware transit point under customer control. Recommended for medium-to-large enterprises with high cloud-to-cloud traffic volumes.
Pattern 3 — Cloud-Native Transit (TGW + vWAN)
Each cloud's native transit hub (AWS TGW, Azure vWAN, GCP NCC) connects to a shared IPsec or private interconnect between clouds. No customer-managed transit infrastructure required — the cloud providers' managed hubs perform the transit function. Lower operational burden, but creates dependency on cloud-provider routing behaviour and limits visibility into transit traffic.
Pattern 4 — SD-WAN Fabric (Full Overlay)
SD-WAN virtual nodes deployed in every cloud region and on-premises site form a unified encrypted overlay fabric. The SD-WAN controller manages all routing policy, encryption, and traffic steering centrally. All sites — cloud, on-premises, branch — are treated uniformly. Highest operational sophistication required to deploy; lowest ongoing complexity once operational. The recommended pattern for enterprises managing 3+ cloud providers with complex traffic policies.
| Pattern | Cloud Providers | Traffic Volume | Ops Complexity | Best Fit |
|---|---|---|---|---|
| 1 — On-Prem Hub | 2–3 | Low–Medium | Low | On-prem heavy; small cloud footprint; existing DC investment |
| 2 — Colo Exchange | 2–4 | Medium–High | Medium | High cloud-to-cloud bandwidth; private circuit requirements; regulated data |
| 3 — Cloud-Native Transit | 2–3 | Low–Medium | Low–Medium | Cloud-first; minimal on-prem; dev/test and non-critical workloads |
| 4 — SD-WAN Fabric | Any | Any | High (initial) / Low (ongoing) | Enterprise-scale; 3+ clouds; on-prem + cloud + branch unification |
11. Vendor and Tool Selection Guide
| Category | Tool / Vendor | Key Capability | Best For |
|---|---|---|---|
| SD-WAN / Overlay | Cisco Catalyst SD-WAN (Viptela) | Full enterprise WAN + multi-cloud overlay; OMP routing; Cloud OnRamp for AWS/Azure/GCP | Cisco-invested enterprises; on-prem + multi-cloud unification |
| Multi-Cloud Networking | Aviatrix | Purpose-built multi-cloud transit; single controller; encrypted tunnels; FireNet for NGFW insertion | Complex multi-cloud with 3+ providers; cloud-native teams |
| SASE / ZTNA | Cisco SSE / Umbrella + ZTNA | User-to-cloud ZTNA, DNS security, CASB for multi-cloud SaaS; Duo device trust | Replacing VPN for user access to multi-cloud workloads |
| Network Exchange | Equinix Fabric / Megaport | Software-defined L2 cross-connects between clouds at colocation facilities; API-provisioned | Private interconnect without owning physical router hardware at colo |
| IaC / Automation | Terraform (multi-provider) | Single HCL codebase managing AWS TGW, Azure vWAN, GCP NCC, and VPN gateways simultaneously | Any organization treating network config as code |
| Observability | Kentik / ThousandEyes | Multi-cloud path visibility, latency analysis, BGP monitoring, cross-cloud flow analytics | Troubleshooting performance issues across cloud boundaries |
12. Frequently Asked Questions
Q: What is the cheapest way to connect AWS to Azure securely?
IPsec VPN between AWS Transit Gateway and Azure VPN Gateway is the lowest-cost option. Configure two tunnels (one per Azure VPN GW instance) with BGP for dynamic routing and IKEv2/AES-256-GCM for encryption. Total cost: AWS TGW attachment (~$36/month) + AWS VPN connection (~$36/month) + Azure VPN Gateway SKU (VpnGw1: ~$140/month) + standard egress fees. Aggregate bandwidth is limited to ~1.25 Gbps per tunnel, so this is appropriate for dev/test or lower-throughput production workloads.
Q: Do I need to encrypt traffic that travels over AWS Direct Connect or Azure ExpressRoute?
It depends on your compliance requirements. Direct Connect and ExpressRoute provide private routing — your traffic does not traverse the public internet. However, they do not provide encryption at the circuit layer. Compliance frameworks like PCI-DSS and HIPAA typically require encryption in transit regardless of whether the link is private. For these workloads, add IPsec VPN over the private circuit (creating an encrypted tunnel inside the private path) or enable MACsec on Dedicated 10G/100G ports where supported.
Q: How do I handle overlapping IP address ranges between cloud environments?
Overlapping CIDRs between VPCs/VNets are one of the most common and hardest-to-fix multi-cloud networking problems. Prevention is far better than remediation: establish a centralised IP Address Management (IPAM) policy before provisioning any cloud environment, assigning non-overlapping RFC1918 blocks to each cloud and region. If you already have overlaps, options include: NAT at the connectivity boundary (introduces operational complexity and breaks end-to-end visibility), re-IP one of the environments (painful but correct), or use an overlay platform like Aviatrix that provides NAT-less connectivity with its own address space.
Q: What is the latency impact of routing traffic between AWS and Azure via my on-premises data center?
Significant. If your data center is in London and your AWS region is us-east-1 (Virginia) and your Azure region is East US (Virginia), a direct AWS-to-Azure path via colocation in Ashburn, VA might add 5–10ms latency. Routing via London adds the transatlantic RTT (~70ms each direction) — turning a 5ms hop into a 150ms round trip. Always use the Pattern 2 (Colo Exchange) or Pattern 3 (Cloud-Native Transit) for latency-sensitive cloud-to-cloud workloads; reserve on-premises transit for management and control plane traffic where latency is less critical.
Q: Can I use a single BGP session to advertise routes to multiple cloud providers simultaneously?
Not directly — each cloud provider requires its own BGP session terminated at its own gateway IP. However, a transit router (physical or SD-WAN virtual appliance) can maintain separate BGP sessions to each cloud provider and redistribute routes between them under policy control. This is exactly what the colo exchange hub and SD-WAN fabric patterns provide. The critical constraint is prefix filtering: you must ensure your transit router does not re-advertise one cloud's prefixes to another without explicit intent and filtering.
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Technical content based on AWS Transit Gateway, AWS Direct Connect, Azure Virtual WAN, Azure ExpressRoute, GCP Network Connectivity Center, and GCP Cloud Interconnect official documentation; Cisco Catalyst SD-WAN Cloud OnRamp design guides; RFC 7519 (JWT), RFC 4301 (IPsec Architecture), and IEEE 802.1AE (MACsec) standards. Bandwidth and pricing figures are indicative and subject to cloud provider changes — verify current specifications at aws.amazon.com, azure.microsoft.com, and cloud.google.com. All content current as of March 2026.
