[[["易于理解","easyToUnderstand","thumb-up"],["解决了我的问题","solvedMyProblem","thumb-up"],["其他","otherUp","thumb-up"]],[["很难理解","hardToUnderstand","thumb-down"],["信息或示例代码不正确","incorrectInformationOrSampleCode","thumb-down"],["没有我需要的信息/示例","missingTheInformationSamplesINeed","thumb-down"],["翻译问题","translationIssue","thumb-down"],["其他","otherDown","thumb-down"]],["最后更新时间 (UTC)：2025-08-12。"],[],[],null,["# Site-to-site data transfer overview\n\nNetwork Connectivity Center lets you use Google's network as part of a wide area network (WAN)\nthat includes your external sites. This feature is known as\n*site-to-site data transfer*.\n\nFor example, suppose you have an office in New York, an office in Sydney, and an\noffice in Tokyo. After completing the required configuration, you can use\nGoogle's network to move data between all three locations.\n\nTo enable this functionality, you use a supported resource to connect each\nsite to Google Cloud. Then you create a Network Connectivity Center\n*spoke* to represent each connectivity resource. Each spoke is attached to a\ncentral *hub*, which provides full mesh connectivity between all of the spokes.\n\nSupported connectivity resources include Cloud VPN\n(HA VPN tunnels), Cloud Interconnect, and\nRouter appliance. Router appliance is a Network Connectivity Center feature that\nlets you install a third-party network virtual appliance in Google Cloud\nand use it to exchange routes with Cloud Router.\n[](/static/network-connectivity/docs/network-connectivity-center/images/data-transfer.svg) Data transfer over Google's network (click to enlarge).\n\nFor a comparison of hybrid connectivity\nproducts and features, see\n[Choosing a Network Connectivity product](/network-connectivity/docs/how-to/choose-product).\n\nFor more information about Router appliance, see the\n[Router appliance overview](/network-connectivity/docs/network-connectivity-center/concepts/ra-overview). For\ninformation about Network Connectivity Center, see the\n[Network Connectivity Center overview](/network-connectivity/docs/network-connectivity-center/concepts/overview).\n\nConsiderations\n--------------\n\nBefore using Network Connectivity Center for data transfer, review and consider the\nfollowing points:\n\n- Data transfer traffic between sites is best-effort, and there are no bandwidth\n or latency guarantees.\n\n- Data transfer is available only in\n [supported locations](/network-connectivity/docs/network-connectivity-center/concepts/locations). For an example of\n how to configure route advertisements when one of your redundant\n Interconnect connections is to an unsupported location, see\n [Configure on-premises router for mixed advertisements](/network-connectivity/docs/network-connectivity-center/concepts/optimal-route-advertisement).\n\n- When data transfer is enabled for one or more spokes, all connectivity\n resources associated with these spokes must be part of a single\n VPC network.\n\n- If you want to exchange routes between spokes in multiple regions, the\n VPC network where your spoke resources are located must have\n its [dynamic routing mode](/vpc/docs/create-modify-vpc-networks#switch-dynamic-routing)\n set to `global`.\n\n- For each spoke, ensure that the\n on-premises router advertises identical routes to the Cloud Router\n associated with the spoke.\n\n- In some cases, your network might experience duplicate route advertisements\n from multiple spokes for the same subnets with the same priority.\n Network Connectivity Center handles these situations as follows:\n\n - When different types of resources are being used, VLAN attachments receive more traffic than Cloud VPN connections, which receive more traffic than VMs acting as router appliance instances.\n - When Network Connectivity Center splits traffic across multiple resources of the same type (for example, two VPN tunnels), it uses equal-cost multi-path ([ECMP](https://en.wikipedia.org/wiki/Equal-cost_multi-path_routing)) routing to distribute traffic.\n- **Known issue.** Problems can occur if there are duplicate route\n advertisements from resources in participating spokes, such as\n HA VPN tunnels, and from similar resources outside\n spokes. When duplicate router advertisements exist, then the traffic in\n participating spokes might use ECMP to distribute traffic across all\n available next hops. This behavior occurs even if the next hops aren't\n participating hubs or spokes themselves.\n\n- [Cloud Router custom learned routes](/network-connectivity/docs/router/concepts/learned-routes) aren't\n honored. If you use custom learned routes on BGP sessions associated with this\n feature, the routes aren't propagated to external sites.\n\n- See also\n [Considerations](/network-connectivity/docs/network-connectivity-center/concepts/overview#considerations)\n in the main Network Connectivity Center overview.\n\nRequirements\n------------\n\nWhen using site-to-site data transfer, you must do all of the following:\n\n- Make sure that all connectivity resources associated with your\n spokes use a high availability configuration. For more information, see\n [High availability for spoke resources](/network-connectivity/docs/network-connectivity-center/concepts/high-availability).\n\n- Follow the guidelines described in\n [ASN requirements for site-to-site data transfer](/network-connectivity/docs/network-connectivity-center/concepts/asn-requirements).\n\n- Make sure that routing prefixes are exclusively advertised within a hub or outside of\n a hub. If you fail to do this, best-path selection might choose a route that\n is not associated with a spoke.\n\nWhat's next\n-----------\n\n- To view a sample topology, see [Sample topology for site-to-site data transfer](/network-connectivity/docs/network-connectivity-center/concepts/data-transfer-topology).\n- To learn more about how Network Connectivity Center enables full mesh connectivity, see [Route exchange with site-to-site data transfer](/network-connectivity/docs/network-connectivity-center/concepts/route-exchange).\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 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 create hubs and spokes, see [Work with hubs and spokes](/network-connectivity/docs/network-connectivity-center/how-to/working-with-hubs-spokes).\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)."]]
