[[["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)：2025-08-18。"],[],[],null,["# Private NAT for Network Connectivity Center spokes\n==================================================\n\nPrivate NAT lets you create a Private NAT\ngateway that works in conjunction with Network Connectivity Center\nspokes to perform network address translation (NAT) between the following\nnetworks:\n\n- Virtual Private Cloud (VPC) networks: In this scenario, the VPC networks that you want to connect are attached to a Network Connectivity Center hub as VPC spokes.\n- VPC networks and networks outside of Google Cloud: In this scenario, one or more VPC networks are attached to a Network Connectivity Center hub as VPC spokes and connected to your on-premises or other cloud provider networks through hybrid spokes.\n\nSpecifications\n--------------\n\nIn addition to the [general Private NAT specifications](/nat/docs/private-nat#pvt-nat-specs),\nPrivate NAT for Network Connectivity Center spokes has the following\nspecifications:\n\n- Private NAT uses a NAT configuration of `type=PRIVATE` to let networks with overlapping subnet IP address ranges communicate. However, only non-overlapping subnets can connect to each other.\n- You need to create a custom NAT rule by referencing a Network Connectivity Center hub. The NAT rule specifies a NAT IP address range from a subnet of purpose `PRIVATE_NAT` that Private NAT uses to perform NAT on traffic between your connected networks.\n- When you create a VM instance in a subnet range where the Private NAT applies, all egress traffic from this VM instance is translated by the gateway if the destination spoke is in the same Network Connectivity Center hub as the gateway. Private NAT translates traffic to destination spokes within the same region as the Private NAT gateway as well as across regions.\n- A Private NAT gateway is associated with subnet IP address ranges in a single region in a single VPC network. This means a Private NAT gateway created in one VPC network doesn't provide NAT services to VMs in other spokes of the Network Connectivity Center hub, even if the VMs are in the same region as the gateway.\n\n### Traffic between VPC networks\n\nThe following additional specifications apply for traffic between\nVPC networks (Inter-VPC NAT):\n\n- To enable Inter-VPC NAT between two VPC networks, each VPC network must be configured as a VPC spoke of a Network Connectivity Center hub. You must ensure that there are no overlapping IP address ranges across your VPC spokes. For more information, see [Create a VPC spoke](/network-connectivity/docs/network-connectivity-center/how-to/working-with-hubs-spokes#create-vpc-spoke).\n- The Network Connectivity Center hub associated with the Private NAT gateway must have at least two VPC spokes, where one of the VPC spokes is the VPC network of the Private NAT gateway.\n- Inter-VPC NAT supports NAT between Network Connectivity Center VPC spokes only, and not between VPC networks connected using VPC Network Peering.\n\n### Traffic between VPC networks and other networks\n\nThe following additional specifications apply for traffic between\nVPC networks and networks outside of Google Cloud:\n\n- The source VPC network must be configured as a VPC spoke of a Network Connectivity Center hub.\n- A hybrid spoke must be attached to the same Network Connectivity Center hub to establish connectivity between the VPC spoke and the destination network outside of Google Cloud. For more information, see [Establishing connectivity between hybrid spokes and VPC spokes](/network-connectivity/docs/network-connectivity-center/concepts/dynamic-route-exchange-with-vpc-spokes#connectivity-between-hybrid-and-vpc-spokes).\n\nFor information about the requirements for using VPC spokes and\nhybrid spokes in the same Network Connectivity Center hub, see\n[Route exchange with VPC spokes](/network-connectivity/docs/network-connectivity-center/concepts/dynamic-route-exchange-with-vpc-spokes).\n\nBasic configuration and workflow\n--------------------------------\n\nThe following diagram shows a basic Private NAT configuration\nfor traffic between two VPC spokes:\n[](/static/nat/images/inter-vpc-nat-flow.png) Inter-VPC NAT translation example (click to enlarge).\n\nIn this example, Private NAT is set up as follows:\n\n- The `pvt-nat-gw` gateway is configured in `vpc-a` to apply to all the IP address ranges of `subnet-a` in the `us-east1` region. Using the NAT IP ranges of `pvt-nat-gw`, a virtual machine (VM) instance in `subnet-a` of `vpc-a` can send traffic to a VM in `subnet-b` of `vpc-b`, even though `subnet-a` of `vpc-a` overlaps with `subnet-c` of `vpc-b`.\n- Both `vpc-a` and `vpc-b` are configured as spokes of a Network Connectivity Center hub.\n- The `pvt-nat-gw` gateway is configured to provide NAT between VPC networks that are configured as VPC spokes in the same Network Connectivity Center hub.\n\n### Example workflow\n\nIn the preceding diagram, `vm-a` with the internal IP address `192.168.1.2` in\n`subnet-a` of `vpc-a` needs to download an update from `vm-b` with the internal\nIP address `192.168.2.2` in `subnet-b` of `vpc-b`. Both the VPC\nnetworks are connected to the same Network Connectivity Center hub as VPC\nspokes. Assume that `vpc-b` contains another subnet `192.168.1.0/24` that overlaps\nwith the subnet in `vpc-a`. For `subnet-a` of `vpc-a` to communicate with `subnet-b`\nof `vpc-b`, you need to configure a Private NAT gateway, `pvt-nat-gw`,\nin `vpc-a` as follows:\n\n- Private NAT subnet: Before configuring the Private NAT\n gateway, create a Private NAT subnet of purpose `PRIVATE_NAT`,\n for example, `10.1.2.0/29`. Ensure that this subnet doesn't overlap\n with an existing subnet in any of the VPC spokes attached to the\n same Network Connectivity Center hub.\n\n- A NAT rule whose `nexthop.hub` matches the Network Connectivity Center hub URL.\n\n- NAT for all address ranges of `subnet-a`.\n\nThe following table summarizes the network configuration specified in the preceding\nexample:\n\nPrivate NAT for Network Connectivity Center spokes follows the\n[port reservation procedure](/nat/docs/ports-and-addresses#port-reservation-procedure)\nto reserve the following NAT source IP address\nand source port tuples for each of the VMs in the network. For example, the\nPrivate NAT gateway reserves 64 source ports for `vm-a`:\n`10.1.2.2:34000` through `10.1.2.2:34063`.\n\nWhen the VM uses the TCP protocol to send a packet to the update server\n`192.168.2.2` on destination port `80`, the following occurs:\n\n1. The VM sends a request packet with these attributes:\n\n - Source IP address: `192.168.1.2`, the internal IP address of the VM\n - Source port: `24000`, the ephemeral source port chosen by the VM's operating system\n - Destination address: `192.168.2.2`, the update server's IP address\n - Destination port: `80`, the destination port for HTTP traffic to the update server\n - Protocol: TCP\n2. The `pvt-nat-gw` gateway performs source network address translation (SNAT or\n source NAT) on egress, rewriting the request\n packet's NAT source IP address and source port:\n\n - NAT source IP address: `10.1.2.2`, from one of the VM's reserved NAT source IP address and source port tuples\n - Source port: `34022`, an unused source port from one of the VM's reserved source port tuples\n - Destination address: `192.168.2.2`, unchanged\n - Destination port: `80`, unchanged\n - Protocol: TCP, unchanged\n3. The update server sends a response packet that arrives on the\n `pvt-nat-gw` gateway with these attributes:\n\n - Source IP address: `192.168.2.2`, the update server's internal IP address\n - Source port: `80`, the HTTP response from the update server\n - Destination address: `10.1.2.2`, which matches the original NAT source IP address of the request packet\n - Destination port: `34022`, which matches the source port of the request packet\n - Protocol: TCP, unchanged\n4. The `pvt-nat-gw` gateway performs destination network address translation\n (DNAT) on the response packet, rewriting the response packet's destination address\n and destination port so that the packet is delivered to the VM that requested the update with the following attributes:\n\n - Source IP address: `192.168.2.2`, unchanged\n - Source port: `80`, unchanged\n - Destination address: `192.168.1.2`, the internal IP address of the VM\n - Destination port: `24000`, matching the original ephemeral source port of the request packet\n - Protocol: TCP, unchanged\n\nWhat's next\n-----------\n\n- Set up [Private NAT for Network Connectivity Center spokes](/nat/docs/set-up-private-nat).\n- Learn about [Cloud NAT product interactions](/nat/docs/nat-product-interactions).\n- Learn about [Cloud NAT addresses and ports](/nat/docs/ports-and-addresses).\n- Learn about [Cloud NAT rules](/nat/docs/nat-rules-overview).\n- Troubleshoot [common issues](/nat/docs/troubleshooting)."]]
