Google Cloud: Cloud Interconnect Overview

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Cloud Interconnect provides low latency, high availability connections that enable you to reliably transfer data between your on-premises and Google Cloud Virtual Private Cloud (VPC) networks. Also, Interconnect connections provide internal IP address communication, which means internal IP addresses are directly accessible from both networks.

Cloud Interconnect offers two options for extending your on-premises network:

  • Dedicated Interconnect provides a direct physical connection between your on-premises network and Google’s network.
  • Partner Interconnect provides connectivity between your on-premises and VPC networks through a supported service provider.

Dedicated Interconnect:

Dedicated Interconnect

Partner Interconnect:

Partner Interconnect


Using Cloud Interconnect provides the following benefits:

  • Traffic between your on-premises network and your VPC network doesn’t traverse the public internet. Traffic traverses a dedicated connection or goes through a service provider with a dedicated connection.
  • Your VPC network’s internal IP addresses are directly accessible from your on-premises network. You don’t need to use a NAT device or VPN tunnel to reach internal IP addresses.
  • You can scale your connection capacity to meet your particular requirements.
  • For Dedicated Interconnect, connection capacity is delivered over one or more 10-Gbps or 100-Gbps Ethernet connections, with the following maximum capacities supported per Interconnect connection:
  • For Partner Interconnect, the following connection capacities for each VLAN attachment are supported:
  • Dedicated Interconnect, Partner Interconnect, Direct Peering, and Carrier Peering can all help you optimize egress traffic from your VPC network and reduce your egress costs. Cloud VPN by itself does not reduce egress costs.
  • You can use Cloud Interconnect with Private Google Access for on-premises hosts so that on-premises hosts can use internal IP addresses rather than external IP addresses to reach Google APIs and services.


Using Cloud VPN instead

If you don’t require the low latency and high availability of Cloud Interconnect, consider using Cloud VPN to set up IPsec VPN tunnels between your networks. IPsec VPN tunnels encrypt data by using industry-standard IPsec protocols as traffic traverses the public internet.

A Cloud VPN tunnel doesn’t require the overhead or costs associated with a direct, private connection. Cloud VPN only requires a VPN device in your on-premises network.

IP addressing and dynamic routes

When you connect your VPC network to your on-premises network, you allow communication between the IP address space of your on-premises network and some or all of the subnets in your VPC network. Which VPC subnets are available depends on the dynamic routing mode of your VPC network. Subnet IP ranges in VPC networks are always internal IP addresses.

The IP address space on your on-premises network and on your VPC network must not overlap, or traffic is not routed properly. Remove any overlapping addresses from either network.

Your on-premises routers share the routes to your on-premises network to the Cloud Routers in your VPC network. This action creates custom dynamic routes in your VPC network, each with a next hop set to the appropriate VLAN attachment.

Cloud Interconnect as a data transfer network

Using Network Connectivity Center, you can use VLAN attachments to connect on-premises networks together, passing traffic between them as a data transfer network. You connect the networks by attaching VLAN attachments to a Network Connectivity Center spoke for each on-premises location. You then connect each spoke to a Network Connectivity Center hub.

Restricting Cloud Interconnect usage

By default, any VPC network can use Cloud Interconnect. To control which VPC networks can use Cloud Interconnect, you can set an organization policy.

Cloud Interconnect MTU

VLAN attachments can have a maximum transmission unit (MTU) of 1440 or 1500 bytes.

  • If your VPC network’s MTU is set to 1500, create VLAN attachments with MTUs set to 1500 as well.
  • If the VLAN attachments in that network have MTUs set to 1440, lower the MTU of the attached VPC network to 1460.

Happy Learning !!!

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