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The following topology shows a VPC network and two on-premises
sites. Each on-premises site connects to Google Cloud by using a
Router appliance spoke. The two on-premises sites can use Google's network
to exchange data with each other.
Router appliance topology (click to enlarge)
On-premises Customer network A and Customer network B are each connected
through customer premises equipment (CPE) to a router appliance instance.
CPEs typically use a connectivity mechanism, such as an SD-WAN overlay tunnel
or an IPsec VPN tunnel, to establish connectivity with the
router appliance instance.
Each router appliance instance is located in the
Google Cloud region closest to its associated customer network. Both
router appliance instances are in a single VPC network.
However, the router appliance instances are in different regions. For this
reason, the VPC network has its
dynamic routing mode
set to global.
Both router appliance instances are attached as spokes to the
Network Connectivity Center hub. Because Customer network A and Customer network B
need to send data to each other, both spokes have the site-to-site data
transfer field enabled.
In each region, a router appliance instance establishes Border Gateway
Protocol (BGP) peering with the appropriate Cloud Router. Each
Cloud Router receives and advertises route prefixes from the
corresponding on-premises location.
The Cloud Routers dynamically exchange all received
routes with each other. This configuration provides end-to-end dynamic route
exchange and data plane connectivity between Customer network A and
Customer network B.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-28 UTC."],[],[],null,["# Sample topology for data transfer\n\nThe following topology shows a VPC network and two on-premises\nsites. Each on-premises site connects to Google Cloud by using a\nRouter appliance spoke. The two on-premises sites can use Google's network\nto exchange data with each other.\n[](/static/network-connectivity/docs/network-connectivity-center/images/router-appliance-topology.svg) Router appliance topology (click to enlarge)\n\n1. On-premises `Customer network A` and `Customer network B` are each connected\n through *customer premises equipment (CPE)* to a router appliance instance.\n CPEs typically use a connectivity mechanism, such as an SD-WAN overlay tunnel\n or an IPsec VPN tunnel, to establish connectivity with the\n router appliance instance.\n\n Each router appliance instance is located in the\n Google Cloud region closest to its associated customer network. Both\n router appliance instances are in a single VPC network.\n However, the router appliance instances are in different regions. For this\n reason, the VPC network has its\n [dynamic routing mode](/vpc/docs/create-modify-vpc-networks#switch-dynamic-routing)\n set to `global`.\n2. Both router appliance instances are attached as spokes to the\n Network Connectivity Center hub. Because `Customer network A` and `Customer network B`\n need to send data to each other, both spokes have the site-to-site data\n transfer field enabled.\n\n *You can use site-to-site data transfer only in supported locations.* For\n more information, see\n [Locations supported for data transfer](/network-connectivity/docs/network-connectivity-center/concepts/locations).\n3. In each region, a router appliance instance establishes Border Gateway\n Protocol (BGP) peering with the appropriate Cloud Router. Each\n Cloud Router receives and advertises route prefixes from the\n corresponding on-premises location.\n\n4. The Cloud Routers dynamically exchange all received\n routes with each other. This configuration provides end-to-end dynamic route\n exchange and data plane connectivity between `Customer network A` and\n `Customer network B`.\n\n | **Important:** For Cloud Routers in different regions to exchange routes with each other, you must enable global dynamic routing mode in your VPC network. For more information, see [Dynamic routing](/vpc/docs/vpc#routing_for_hybrid_networks).\n\nWhat's next\n-----------\n\n- To learn about high availability requirements, see [High availability requirements for spoke resources](/network-connectivity/docs/network-connectivity-center/concepts/high-availability).\n- To learn about requirements for assigning ASNs, see [ASN requirements for site-to-site data transfer](/network-connectivity/docs/network-connectivity-center/concepts/asn-requirements).\n- To create hubs and spokes, see [Working with hubs and spokes](/network-connectivity/docs/network-connectivity-center/how-to/working-with-hubs-spokes).\n- To work through a tutorial, see [Connecting two sites by using Cloud VPN spokes](/network-connectivity/docs/network-connectivity-center/tutorials/connecting-two-offices-with-vpns).\n- To view a list of partners whose solutions are integrated with Network Connectivity Center, see [Network Connectivity Center partners](/network-connectivity/docs/network-connectivity-center/partners)."]]
