This topic describes how to use Alibaba Cloud SDK for Python to create an SNAT entry.

Prerequisites

Before you use Alibaba Cloud SDK for Python, make sure that the following requirements are met:
  • An Alibaba Cloud account and the AccessKey pair are obtained. You can create and view your AccessKey pair on the Security Management page of the Alibaba Cloud Management Console.
  • Make sure that Alibaba Cloud SDK for Python is installed. For more information, see aliyun-python-sdk-vpc 3.0.12.
  • The VPC Python example library is downloaded.
    Go to the directory where the setup.py file is stored, and run the following command to initialize the environment: 
    python setup.py install

Background information

The sample code in this topic includes the following operations:
  1. Create a virtual private cloud (VPC) in the China (Shanghai) region.
  2. Create a vSwitch for the VPC.
  3. Create a NAT gateway in the VPC.
  4. Create an elastic IP address (EIP) in the China (Shanghai) region.
  5. Associate the EIP with the NAT gateway.
  6. Create an SNAT entry.
  7. Query the EIP that is associated with the NAT gateway.
  8. Query the NAT gateway.
  9. Delete the SNAT entry.
  10. Disassociate the EIP from the NAT gateway.
  11. Delete the NAT gateway.
  12. Release the EIP.
  13. Delete the vSwitch.
  14. Delete the VPC.

Procedure

  1. In the directory of downloaded SDK files, open the aliyun-openapi-python-sdk-examples\sdk_examples\examples\natgw folder.
  2. Open the natgw_snat.py file in your text editor. Set the required parameters, save the configurations, and then exit the editor.
    The following sample code is displayed: 
    #encoding=utf-8
import sys
import json
import time

from aliyunsdkcore.acs_exception.exceptions import ServerException, ClientException
from aliyunsdkvpc.request.v20160428 import CreateNatGatewayRequest
from aliyunsdkvpc.request.v20160428 import DeleteNatGatewayRequest
from aliyunsdkvpc.request.v20160428 import DescribeNatGatewaysRequest
from aliyunsdkvpc.request.v20160428 import CreateSnatEntryRequest
from aliyunsdkvpc.request.v20160428 import DescribeSnatTableEntriesRequest
from aliyunsdkvpc.request.v20160428 import DeleteSnatEntryRequest
from sdk_lib.sdk_vpc import Vpc
from sdk_lib.sdk_vswitch import VSwitch
from sdk_lib.sdk_eip import Eip
from sdk_lib.sdk_cbwp import CommonBandwidthPackage
from sdk_lib.common_util import CommonUtil
from sdk_lib.check_status import CheckStatus
from sdk_lib.exception import ExceptionHandler
from sdk_lib.consts import *

client = ACS_CLIENT = AcsClient(
    'accessKeyId',
    'accessSecret',
    'RegionId'
    #timeout = 35
)


class NatGateway(object):
    def __init__(self, client):
        self.client = client

    def create_nat_gateway(self, params):
        """
        create_nat_gateway: Create a NAT gateway
        """
        try:
            request = CreateNatGatewayRequest.CreateNatGatewayRequest()
            request.set_VpcId(params['vpc_id'])
            response = client.do_action_with_exception(request)
            response_json = json.loads(response)
            # Check whether the NAT gateway is in the Available state
            if CheckStatus.check_status(TIME_DEFAULT_OUT, DEFAULT_TIME,
                                        self.describe_nat_gateway_status,
                                        AVAILABLE, response_json['NatGatewayId']):
                return response_json
        except ServerException as e:
            ExceptionHandler.server_exception(e)
        except ClientException as e:
            ExceptionHandler.client_exception(e)

    def describe_nat_gateway(self, nat_gateway_id):
        """
        describe_nat_gateway: Query information about NAT gateways in the specified region
        """
        try:
            request = DescribeNatGatewaysRequest.DescribeNatGatewaysRequest()
            request.set_NatGatewayId(nat_gateway_id)
            response = client.do_action_with_exception(request)
            response_json = json.loads(response)
            return response_json
        except ServerException as e:
            ExceptionHandler.server_exception(e)
        except ClientException as e:
            ExceptionHandler.client_exception(e)

    def delete_nat_gateway(self, params):
        """
        delete_nat_gateway: Delete the NAT gateway
        """
        try:
            request = DeleteNatGatewayRequest.DeleteNatGatewayRequest()
            request.set_NatGatewayId(params['nat_gateway_id'])
            response = client.do_action_with_exception(request)
            response_json = json.loads(response)
            # Check whether the NAT gateway is in the Available state
            if CheckStatus.check_status(TIME_DEFAULT_OUT, DEFAULT_TIME * 5,
                                        self.describe_nat_gateway_status,
                                        '', params['nat_gateway_id']):
                return response_json
        except ServerException as e:
            ExceptionHandler.server_exception(e)
        except ClientException as e:
            ExceptionHandler.client_exception(e)

    def describe_nat_gateway_status(self, nat_gateway_id):
        """
        describe_nat_gateway_status: Query the status of NAT gateways in the specified region
        """
        response = self.describe_nat_gateway(nat_gateway_id)
        if len(response["NatGateways"]["NatGateway"]) == 0:
            return ''
        return response["NatGateways"]["NatGateway"][0]['Status']

    def create_snat_entry(self, params):
        """
        describe_snat: Create an SNAT entry
        """
        try:
            request = CreateSnatEntryRequest.CreateSnatEntryRequest()
            request.set_SnatTableId(params['snat_table_id'])
            request.set_SourceVSwitchId(params['vswitch_id'])
            request.set_SnatIp(params['snat_ip'])
            response = client.do_action_with_exception(request)
            response_json = json.loads(response)
            # Check whether the SNAT entry is in the Available state
            if CheckStatus.check_status(TIME_DEFAULT_OUT, DEFAULT_TIME,
                                        self.describe_snat_status,
                                        AVAILABLE, params['snat_table_id']):
                return response_json
        except ServerException as e:
            ExceptionHandler.server_exception(e)
        except ClientException as e:
            ExceptionHandler.client_exception(e)

    def describe_snat(self, snat_table_id):
        """
        describe_snat: Query information about SNAT entries created in the specified region l
        """
        try:
            request = DescribeSnatTableEntriesRequest.DescribeSnatTableEntriesRequest()
            request.set_SnatTableId(snat_table_id)
            response = client.do_action_with_exception(request)
            response_json = json.loads(response)
            return response_json
        except ServerException as e:
            ExceptionHandler.server_exception(e)
        except ClientException as e:
            ExceptionHandler.client_exception(e)

    def describe_snat_status(self, snat_table_id):
        """
        describe_snat_status: Query the status of SNAT entries created in the specified region
        """
        response = self.describe_snat(snat_table_id)
        if len(response["SnatTableEntries"]["SnatTableEntry"]) == 0:
            return ''
        return response["SnatTableEntries"]["SnatTableEntry"][0]['Status']

    def delete_snat_entry(self, params):
        """
        delete_snat_entry: Delete the SNAT entry
        """
        try:
            request = DeleteSnatEntryRequest.DeleteSnatEntryRequest()
            request.set_SnatTableId(params['snat_table_id'])
            request.set_SnatEntryId(params['snat_entry_id'])
            response = client.do_action_with_exception(request)
            response_json = json.loads(response)
            # Check whether the SNAT entry is in the Available state
            if CheckStatus.check_status(TIME_DEFAULT_OUT, DEFAULT_TIME * 5,
                                        self.describe_snat_status,
                                        '', params['snat_table_id']):
                return response_json
        except ServerException as e:
            ExceptionHandler.server_exception(e)
        except ClientException as e:
            ExceptionHandler.client_exception(e)


def main():
    vpc = Vpc(client)
    vswitch = VSwitch(client)
    eip = Eip(client)
    cbwp = CommonBandwidthPackage(client)
    nat_gateway = NatGateway(client)

    params = {}

    # Create a VPC
    vpc_json = vpc.create_vpc()
    CommonUtil.log("create_vpc", vpc_json)

    # Create a vSwitch
    params['vpc_id'] = vpc_json['VpcId']
    params['zone_id'] = "cn-hangzhou-d"
    params['cidr_block'] = "172.16.1.0/24"
    vswitch_json = vswitch.create_vswitch(params)
    CommonUtil.log("create_vswitch", vswitch_json)
    params['vswitch_id'] = vswitch_json['VSwitchId']

    # Create a NAT gateway
    nat_gateway_json = nat_gateway.create_nat_gateway(params)
    CommonUtil.log("create_nat_gateway", nat_gateway_json)

    # Create an EIP
    eip_response_json = eip.allocate_eip_address(params)
    CommonUtil.log("allocate_eip_address", eip_response_json)
    params['allocation_id'] = eip_response_json["AllocationId"]
    params['snat_ip'] = eip_response_json['EipAddress']

    # Associate the EIP with the NAT gateway
    params['instance_id'] = nat_gateway_json['NatGatewayId']
    params['allocation_id'] = eip_response_json["AllocationId"]
    params['instance_type'] = 'Nat'
    eip_response_json = eip.associate_eip_address(params)
    CommonUtil.log("associate_eip_address eip", eip_response_json)

    # Create an SNAT entry
    params['snat_table_id'] = nat_gateway_json['SnatTableIds']['SnatTableId'][0]
    snat_entry_json = nat_gateway.create_snat_entry(params)
    CommonUtil.log("create_snat_entry", snat_entry_json)

    # Query the EIP
    eip_response_json = eip.describe_eip_address(params['allocation_id'])
    CommonUtil.log("describe_eip_address", eip_response_json)

    # Query NAT gateways
    params['nat_gateway_id'] = nat_gateway_json['NatGatewayId']
    nat_gateway_json = nat_gateway.describe_nat_gateway(params['nat_gateway_id'])
    CommonUtil.log("describe_nat_gateway", nat_gateway_json)

    # Delete the SNAT entry
    params['snat_entry_id'] = snat_entry_json['SnatEntryId']
    snat_entry_json = nat_gateway.delete_snat_entry(params)
    CommonUtil.log("delete_snat_entry", snat_entry_json)

    # Disassociate the EIP from the NAT gateway
    eip_response_json = eip.unassociate_eip_address(params)
    CommonUtil.log("unassociate_eip_address nat", eip_response_json)

    # Delete the NAT gateway
    nat_gateway_json = nat_gateway.delete_nat_gateway(params)
    CommonUtil.log("delete_nat_gateway", nat_gateway_json)

    # Release the EIP
    eip_response_json = eip.release_eip_address(params)
    CommonUtil.log("release_eip_address", eip_response_json)

    # Delete the vSwitch
    params['vswitch_id'] = vswitch_json['VSwitchId']
    vswitch_json = vswitch.delete_vswitch(params)
    CommonUtil.log("delete_vswitch", vswitch_json)

    # Delete the VPC
    vpc_json = vpc.delete_vpc(params)
    CommonUtil.log("delete_vpc", vpc_json)


if __name__ == "__main__":
    sys.exit(main())
  3. Go to the directory where the natgw_snat.py file is stored and run the following command to create an SNAT entry: 
    python natgw_snat.py

Result

The following output is returned:
---------------------------create_vpc---------------------------
{
  "ResourceGroupId": "rg-acfmxazxxxxxxxx",
  "RouteTableId": "vtb-uf6a8ccj9ne58xxxxxxxx",
  "VRouterId": "vrt-uf6qqqaf1o1ptxxxxxxxx",
  "VpcId": "vpc-uf6hxer3h07wgxxxxxxxx",
  "RequestId": "8F483A7B-8A38-47ED-85BD-1E83C075AEA4"
}

---------------------------create_vswitch---------------------------
{
  "VSwitchId": "vsw-uf6lbov9tyetqxxxxxxxx",
  "RequestId": "2EE2E11B-EF60-4C88-BE2A-F45517290B31"
}

---------------------------create_nat_gateway---------------------------
{
  "NatGatewayId": "ngw-uf6l3c3rswubuxxxxxxxx",
  "BandwidthPackageIds": {
    "BandwidthPackageId": []
  },
  "ForwardTableIds": {
    "ForwardTableId": [
      "ftb-uf6086r1hyecbxxxxxxxx"
    ]
  },
  "RequestId": "9037D769-24C8-46AD-83F3-4C0538FA5970",
  "SnatTableIds": {
    "SnatTableId": [
      "stb-uf6ppo11rsecmxxxxxxxx"
    ]
  }
}

---------------------------allocate_eip_address---------------------------
{
  "EipAddress": "101.xx.xx.110",
  "ResourceGroupId": "rg-acfmxazxxxxxxxx",
  "RequestId": "0DE621B4-6BDE-4E17-A294-8F71FBB9F710",
  "AllocationId": "eip-uf6d311cpmr0nxxxxxxxx"
}

---------------------------associate_eip_address eip---------------------------
{
  "RequestId": "C95B2EDC-F081-4784-B60B-2600F60E684D"
}

---------------------------create_snat_entry---------------------------
{
  "SnatEntryId": "snat-uf6ppbwshdu40xxxxxxxx",
  "RequestId": "BB9F8FD2-3CB5-4F84-8006-FE64BF3BEA06"
}

---------------------------describe_eip_address---------------------------
{
  "TotalCount": 1,
  "PageNumber": 1,
  "PageSize": 10,
  "EipAddresses": {
    "EipAddress": [
      {
        "ISP": "BGP",
        "ExpiredTime": "",
        "InternetChargeType": "PayByBandwidth",
        "IpAddress": "101.xx.xx.110",
        "AllocationId": "eip-uf6d311cpmr0nxxxxxxxx",
        "PrivateIpAddress": "",
        "Status": "InUse",
        "BandwidthPackageId": "",
        "InstanceId": "ngw-uf6l3c3rswubuxxxxxxxx",
        "InstanceRegionId": "cn-shanghai",
        "RegionId": "cn-shanghai",
        "AvailableRegions": {
          "AvailableRegion": [
            "cn-shanghai"
          ]
        },
        "ResourceGroupId": "rg-acfmxazxxxxxxxx",
        "HasReservationData": false,
        "InstanceType": "Nat",
        "AllocationTime": "2019-04-24T11:20:09Z",
        "Name": "",
        "OperationLocks": {
          "LockReason": []
        },
        "Mode": "NAT",
        "BandwidthPackageType": "",
        "BandwidthPackageBandwidth": "",
        "Bandwidth": "5",
        "HDMonitorStatus": "OFF",
        "ChargeType": "PostPaid",
        "SecondLimited": false,
        "Descritpion": ""
      }
    ]
  },
  "RequestId": "19052237-6E84-4258-89B9-05772C33C0DC"
}

---------------------------describe_nat_gateway---------------------------
{
  "TotalCount": 1,
  "PageNumber": 1,
  "RequestId": "26CAA3FE-B400-4522-9582-2DAAF69129AE",
  "PageSize": 10,
  "NatGateways": {
    "NatGateway": [
      {
        "Status": "Available",
        "BandwidthPackageIds": {
          "BandwidthPackageId": []
        },
        "VpcId": "vpc-uf6hxer3h07wgxxxxxxxx",
        "Description": "",
        "ForwardTableIds": {
          "ForwardTableId": [
            "ftb-uf6086r1hyecbxxxxxxxx"
          ]
        },
        "IpLists": {
          "IpList": [
            {
              "UsingStatus": "UsedBySnatTable",
              "IpAddress": "101.xx.xx.110",
              "AllocationId": "eip-uf6d311cpmr0nxxxxxxxx"
            }
          ]
        },
        "BusinessStatus": "Normal",
        "RegionId": "cn-shanghai",
        "CreationTime": "2019-04-24T11:20:06Z",
        "NatGatewayId": "ngw-uf6l3c3rswubuxxxxxxxx",
        "SnatTableIds": {
          "SnatTableId": [
            "stb-uf6ppo11rsecmxxxxxxxx"
          ]
        },
        "AutoPay": false,
        "InstanceChargeType": "PostPaid",
        "ExpiredTime": "",
        "Spec": "Small",
        "Name": ""
      }
    ]
  }
}

---------------------------delete_snat_entry---------------------------
{
  "RequestId": "CDA82881-ACF0-4DD1-887B-A764F56F180D"
}

---------------------------unassociate_eip_address nat--------------------------
-
{
  "RequestId": "140C46FF-0DB0-47F9-B0F4-3459DF117EAF"
}

---------------------------delete_nat_gateway---------------------------
{
  "RequestId": "8709747C-6786-443C-8AEA-51647AA49769"
}

---------------------------release_eip_address---------------------------
{
  "RequestId": "0BC21C23-0FB3-4594-8B14-6552DF788C93"
}

---------------------------delete_vswitch---------------------------
{
  "RequestId": "16E840EC-E058-40C1-A5BF-8CDF672EA139"
}

---------------------------delete_vpc---------------------------
{
  "RequestId": "B5F18126-FF2A-4005-9973-3984034DF0F4"
}