[[["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,["# Classic VPN topologies\n\nWith Classic VPN, your on-premises hosts communicate through\none or more IPsec VPN tunnels to Compute Engine virtual machine (VM) instances\nin your project's Virtual Private Cloud (VPC) networks.\n\nClassic VPN supports site-to-site VPN as the sample topology\nshown on this page or with [redundancy options](#redundancy-options).\n| **Note:** For information about HA VPN topologies, including Google Cloud-to-Google Cloud VPNs, see the [HA VPN topologies page](/network-connectivity/docs/vpn/concepts/topologies). For information about configuring third-party devices or services with Cloud VPN, see [Use third-party VPNs](/network-connectivity/docs/vpn/how-to/interop-guides).\n\nSample Classic VPN topology\n---------------------------\n\nThe following diagram shows a sample VPN\n[connection](/network-connectivity/docs/vpn/concepts/key-terms#connection)\nbetween a Classic VPN gateway and your\n[peer](/network-connectivity/docs/vpn/concepts/key-terms#peer-definition) VPN gateway.\n[](/static/network-connectivity/docs/vpn/images/cloud-vpn-overview-01.svg) Sample VPN topology with a connection between a Classic VPN gateway and your peer VPN gateway (click to enlarge).\n\nRedundancy and failover options\n-------------------------------\n\n| **Note:** With Classic VPN, it is not possible to create two VPN tunnels within the same Cloud VPN gateway to the same destination VPN gateway.\n\nYou can provide redundancy and failover for Classic VPN gateways\nby using a second Classic VPN gateway.\n\n### Use a second peer VPN gateway\n\nFor Classic VPN, if your on-premises side is hardware based, having\na second peer VPN gateway provides redundancy and failover on that side\nof the connection. A second physical gateway lets you take one of the gateways\noffline for software upgrades or other scheduled maintenance. It also protects\nyou in case of an outright failure in one of the devices.\n\nTo configure a tunnel from your Cloud VPN gateway to a\nsecond on-premises-side VPN gateway, do the following:\n\n1. Configure a second on-premises VPN gateway and a tunnel.\n2. Set up a second tunnel on your Cloud VPN gateway pointing to the second on-premises gateway.\n3. Forward the same routes for the second tunnel as you did for the first. If you want both tunnels to balance traffic, set their [route priorities](/vpc/docs/routes) to be the same. If you want one tunnel to be primary, set a lower priority on the second tunnel.\n4. If either VPN tunnel fails due to network issues along the path, or a problem with an on-premises gateway, the Cloud VPN gateway will continue sending traffic over the healthy tunnel and will automatically resume using both tunnels once the failed tunnel recovers.\n\nFor details about configuring redundancy with dynamic routing, see the\n[Cloud Router redundancy page](/network-connectivity/docs/router/concepts/how-cloud-router-works).\n[](/static/network-connectivity/docs/vpn/images/vpn-basic-2-on-prem.svg) Redundant on-premises VPN gateways diagram (click to enlarge)\n\nIncreased throughput and load balancing options\n-----------------------------------------------\n\n| **Note:** the solutions in this section for increasing throughput can be also used to load balance between two gateways as described for each option.\n\nFor information about VPN bandwidth, see the\n[VPN Overview](/network-connectivity/docs/vpn/concepts/overview#network-bandwidth) and [Calculating\nnetwork throughput](/community/tutorials/network-throughput).\n\nThere are three options for scaling a Cloud VPN configuration:\n\n- Option 1: Scale the on-premises VPN gateway.\n- Option 2: Scale the Cloud VPN gateway. If your on-premises VPN gateway's throughput capabilities are higher, and you want to scale higher throughput from the Cloud VPN gateway, you can set up a second Cloud VPN gateway.\n- Option 3: Scale both the on-premises VPN gateway and the Cloud VPN gateway.\n\n### Option 1: Scale the on-premises VPN gateway\n\nSet up a second on-premises VPN gateway device with a different external IP\naddress. Create a second tunnel on your existing Cloud VPN gateway\nthat forwards the same IP range, but pointing at the second on-premises gateway\nIP. Your Cloud VPN gateway automatically load balances between the\nconfigured tunnels. You can set up the VPN gateways to have multiple tunnels\nload balanced this way to increase the aggregate VPN connectivity throughput.\n[](/static/network-connectivity/docs/vpn/images/vpn-basic-2-on-prem.svg) Redundant on-premises VPN gateways diagram (click to enlarge)\n\n### Option 2: Scale the Cloud VPN gateway\n\n| **Note:** This configuration requires an on-premises VPN gateway that supports using equal-cost multi-path routing ([ECMP](https://wikipedia.org/wiki/Equal-cost_multi-path_routing)) between two tunnels having the same on-premises IP ranges. Many software VPNs are not capable of this.\n\nAdd a second\nCloud VPN gateway in the same region as the existing VPN gateway. The second Cloud VPN gateway can have a tunnel that points to\nthe same IP address of the on-premises VPN gateway as the tunnel on the first\ngateway. Once configured, traffic to the on-premises VPN gateway is\nautomatically load balanced between the two Cloud VPN gateways and\ntunnels.\n[](/static/network-connectivity/docs/vpn/images/vpn-basic-2-cloud-vpn.svg) Redundant Cloud VPN gateways diagram (click to enlarge)\n\n### Option 3: Scale both the on-premises VPN gateway and the Cloud VPN gateway\n\n| **Note:** This configuration requires an on-premises VPN gateway that supports using equal-cost multi-path routing ([ECMP](https://wikipedia.org/wiki/Equal-cost_multi-path_routing)) between two tunnels having the same on-premises IP ranges. Many software VPNs are not capable of this.\n\nCombine options 1 and 2 mentioned above to scale throughput. If you have\ntwo on-premises VPN gateways and two Cloud VPN gateways, each\nCloud VPN gateway can have a tunnel pointing at each on-premises\nVPN gateway external IP, giving you four load balanced tunnels between the VPN\ngateway, thereby potentially providing four times the bandwidth.\n[](/static/network-connectivity/docs/vpn/images/vpn-basic-2-cloud-on-prem.svg) Redundant Cloud VPN and on-premises VPN gateways diagram (click to enlarge)\n\nFor more information, see the tutorial\n[Building high-throughput VPNs](/solutions/building-high-throughput-vpns).\nYou can increase the number of tunnels up to your project's quota. ECMP is used\nto balance traffic between tunnels.\n\nWhat's next\n-----------\n\n- To move to HA VPN, see [Move to HA VPN](/network-connectivity/docs/vpn/how-to/moving-to-ha-vpn).\n- To use high-availability and high-throughput scenarios or multiple subnet scenarios, see [Advanced configurations](/network-connectivity/docs/vpn/concepts/advanced).\n- To help you solve common issues that you might encounter when using Cloud VPN, see [Troubleshooting](/network-connectivity/docs/vpn/support/troubleshooting)."]]
