Connect VPCs

Choose the right connection method

• When choosing between VPC peering and CEN, consider:

  • Scale : Use VPC peering connection for small networks (2-3 VPCs) and CEN for large ones (>3 VPCs).

  • Features: To use multicast, service chaining, or cross-region QoS, or to automatically configure routes, use CEN.

  • Cost: For same-region VPCs, use VPC peering connection—intra-region connections are free.

  • Bandwidth: For high-bandwidth intra-region needs, use VPC peering connection—no bandwidth cap applies.

• Key differences:

  Item	VPC peering connection	CEN
  Connection mode	Full-mesh: direct connections between each pair of VPCs	Hub-spoke: VPCs attach to a central Transit Router (TR)
  Number of VPCs	Up to 10 VPCs in the same region Up to 20 across regions	A single TR supports up to 1,000 VPCs
  Route configuration	Manual configuration required for each VPC	Routes can be automatically configured using route learning and route synchronization.
  Scalability	Low Each new VPC requires manual setup and routing	High Add a new VPC by attaching it to the TR, no manual routing needed
  Bandwidth	Intra-region: unlimited Inter-region: default limit 1,024 Mbps	Intra-region: see Maximum bandwidth supported by connections. Inter-region: pay-as-you-go ( quota -limited) or allocated from a bandwidth plan
  Billing	Intra-region: free Inter-region: outbound traffic fees via Cloud Data Transfer (CDT).	Intra-region: connection and processing fees Inter-region: connection, traffic, and bandwidth fees; see CEN billing

Use case examples

1. Connect two VPCs

To connect two Elastic Compute Service (ECS) instances in different VPCs, VPC peering connection is ideal.

Intra-region VPC peering is free.

2. Connect multiple VPCs

For more than two VPCs, peering requires:

• A direct connection between every pair of VPCs (full mesh)

• Manual route configuration for each connection

Complexity grows with VPC count.

CEN  simplifies this:

• Attach all VPCs to a TR

• Full-mesh connectivity is established automatically

• Routes are synchronized without manual intervention

Reduce costs in complex network architectures

In complex multi-region deployments, combining VPC peering and CEN optimizes cost, performance, and control.

Example scenario

A company with multi-region VPCs wants to:

• Connect VPCs across regions

• Control routing policies

• Minimize costs

Recommended solution

• Inter-region connections:

  • Use inter-region VPC peering connection for cost sensitive links (such as between VPC A and VPC C) with no additional cost.

  • For high-bandwidth or dedicated connections, use CEN with bandwidth plans.

• Centralized routing:

  • Connect transit VPCs to CEN to enable inter-region connectivity with granular routing control.

This hybrid approach balances cost and agility.