Configure IPsec/IKE policy for site-to-site VPN connections
This article describes the steps to configure an IPsec/IKE policy for site-to-site (S2S) VPN connections in Azure Stack Hub.
IPsec and IKE policy parameters for VPN gateways
The IPsec and IKE protocol standard supports a wide range of cryptographic algorithms in various combinations. To see which parameters are supported in Azure Stack Hub so you can satisfy your compliance or security requirements, see IPsec/IKE parameters.
This article provides instructions on how to create and configure an IPsec/IKE policy and apply it to a new or existing connection.
Considerations
Note the following important considerations when using these policies:
The IPsec/IKE policy only works on the Standard and HighPerformance (route-based) gateway SKUs.
You can only specify one policy combination for a given connection.
You must specify all algorithms and parameters for both IKE (Main Mode) and IPsec (Quick Mode). Partial policy specification is not allowed.
Consult with your VPN device vendor specifications to ensure the policy is supported on your on-premises VPN devices. Site-to-site connections cannot be established if the policies are incompatible.
Prerequisites
Before you begin, make sure you have the following prerequisites:
An Azure subscription. If you don't already have an Azure subscription, you can activate your MSDN subscriber benefits, or sign up for a free account.
The Azure Resource Manager PowerShell cmdlets. For more info about installing the PowerShell cmdlets, see Install PowerShell for Azure Stack Hub.
Part 1 - Create and set IPsec/IKE policy
This section describes the steps required to create and update the IPsec/IKE policy on a site-to-site VPN connection:
Create a virtual network and a VPN gateway.
Create a local network gateway for cross-premises connection.
Create an IPsec/IKE policy with selected algorithms and parameters.
Create an IPSec connection with the IPsec/IKE policy.
Add/update/remove an IPsec/IKE policy for an existing connection.
The instructions in this article help you set up and configure IPsec/IKE policies, as shown in the following figure:
Part 2 - Supported cryptographic algorithms and key strengths
The following table lists the supported cryptographic algorithms and key strengths configurable by Azure Stack Hub:
| IPsec/IKEv2 | Options |
|---|---|
| IKEv2 Encryption | AES256, AES192, AES128, DES3, DES |
| IKEv2 Integrity | SHA384, SHA256, SHA1, MD5 |
| DH Group | ECP384, DHGroup14, DHGroup2, DHGroup1, ECP256*, DHGroup24* |
| IPsec Encryption | GCMAES256, GCMAES192, GCMAES128, AES256, AES192, AES128, DES3, DES, None |
| IPsec Integrity | GCMAES256, GCMAES192, GCMAES128, SHA256 |
| PFS Group | PFS24, ECP384, ECP256, PFS2048, PFS2, PFS1, PFSMM, None |
| QM SA Lifetime | (Optional: default values are used if not specified) Seconds (integer; min. 300/default 27000 seconds) KBytes (integer; min. 1024/default 102400000 KBytes) |
| Traffic Selector | Policy-based Traffic Selectors are not supported in Azure Stack Hub. |
Note
Setting the QM SA lifetime too low requires unnecessary rekeying, which can degrade performance.
* These parameters are only available in builds 2002 and later.
Your on-premises VPN device configuration must match or contain the following algorithms and parameters that you specify on the Azure IPsec/IKE policy:
- IKE encryption algorithm (Main Mode/Phase 1).
- IKE integrity algorithm (Main Mode/Phase 1).
- DH Group (Main Mode/Phase 1).
- IPsec encryption algorithm (Quick Mode/Phase 2).
- IPsec integrity algorithm (Quick Mode/Phase 2).
- PFS Group (Quick Mode/Phase 2).
- The SA lifetimes are local specifications only and do not need to match.
If GCMAES is used as the IPsec encryption algorithm, you must select the same GCMAES algorithm and key length for IPsec integrity; for example, using GCMAES128 for both.
In the preceding table:
- IKEv2 corresponds to Main Mode or Phase 1.
- IPsec corresponds to Quick Mode or Phase 2.
- DH Group specifies the Diffie-Hellmen Group used in Main Mode or Phase 1.
- PFS Group specifies the Diffie-Hellmen Group used in Quick Mode or Phase 2.
IKEv2 Main Mode SA lifetime is fixed at 28,800 seconds on the Azure Stack Hub VPN gateways.
The following table lists the corresponding Diffie-Hellman Groups supported by the custom policy:
| Diffie-Hellman Group | DHGroup | PFSGroup | Key length |
|---|---|---|---|
| 1 | DHGroup1 | PFS1 | 768-bit MODP |
| 2 | DHGroup2 | PFS2 | 1024-bit MODP |
| 14 | DHGroup14 DHGroup2048 |
PFS2048 | 2048-bit MODP |
| 19 | ECP256* | ECP256 | 256-bit ECP |
| 20 | ECP384 | ECP384 | 384-bit ECP |
| 24 | DHGroup24* | PFS24 | 2048-bit MODP |
* These parameters are only available in builds 2002 and above.
For more information, see RFC3526 and RFC5114.
Part 3 - Create a new site-to-site VPN connection with IPsec/IKE policy
This section walks through the steps to create a site-to-site VPN connection with an IPsec/IKE policy. The following steps create the connection, as shown in the following figure:
For more detailed step-by-step instructions for creating a site-to-site VPN connection, see Create a site-to-site VPN connection.
Step 1 - Create the virtual network, VPN gateway, and local network gateway
1. Declare variables
For this exercise, start by declaring the following variables. Be sure to replace the placeholders with your own values when configuring for production:
$Sub1 = "<YourSubscriptionName>"
$RG1 = "TestPolicyRG1"
$Location1 = "East US 2"
$VNetName1 = "TestVNet1"
$FESubName1 = "FrontEnd"
$BESubName1 = "Backend"
$GWSubName1 = "GatewaySubnet"
$VNetPrefix11 = "10.11.0.0/16"
$VNetPrefix12 = "10.12.0.0/16"
$FESubPrefix1 = "10.11.0.0/24"
$BESubPrefix1 = "10.12.0.0/24"
$GWSubPrefix1 = "10.12.255.0/27"
$DNS1 = "8.8.8.8"
$GWName1 = "VNet1GW"
$GW1IPName1 = "VNet1GWIP1"
$GW1IPconf1 = "gw1ipconf1"
$Connection16 = "VNet1toSite6"
$LNGName6 = "Site6"
$LNGPrefix61 = "10.61.0.0/16"
$LNGPrefix62 = "10.62.0.0/16"
$LNGIP6 = "131.107.72.22"
2. Connect to your subscription and create a new resource group
Make sure you switch to PowerShell mode to use the Resource Manager cmdlets. For more information, see Connect to Azure Stack Hub with PowerShell as a user.
Open your PowerShell console and connect to your account; for example:
Connect-AzAccount
Select-AzSubscription -SubscriptionName $Sub1
New-AzResourceGroup -Name $RG1 -Location $Location1
3. Create the virtual network, VPN gateway, and local network gateway
The following example creates the virtual network, TestVNet1, along with three subnets and the VPN gateway. When substituting values, it's important that you specifically name your gateway subnet GatewaySubnet. If you name it something else, your gateway creation fails.
$fesub1 = New-AzVirtualNetworkSubnetConfig -Name $FESubName1 -AddressPrefix $FESubPrefix1
$besub1 = New-AzVirtualNetworkSubnetConfig -Name $BESubName1 -AddressPrefix $BESubPrefix1
$gwsub1 = New-AzVirtualNetworkSubnetConfig -Name $GWSubName1 -AddressPrefix $GWSubPrefix1
New-AzVirtualNetwork -Name $VNetName1 -ResourceGroupName $RG1 -Location $Location1 -AddressPrefix $VNetPrefix11,$VNetPrefix12 -Subnet $fesub1,$besub1,$gwsub1
$gw1pip1 = New-AzPublicIpAddress -Name $GW1IPName1 -ResourceGroupName $RG1 -Location $Location1 -AllocationMethod Dynamic
$vnet1 = Get-AzVirtualNetwork -Name $VNetName1 -ResourceGroupName $RG1
$subnet1 = Get-AzVirtualNetworkSubnetConfig -Name "GatewaySubnet" `
-VirtualNetwork $vnet1
$gw1ipconf1 = New-AzVirtualNetworkGatewayIpConfig -Name $GW1IPconf1 `
-Subnet $subnet1 -PublicIpAddress $gw1pip1
New-AzVirtualNetworkGateway -Name $GWName1 -ResourceGroupName $RG1 `
-Location $Location1 -IpConfigurations $gw1ipconf1 -GatewayType Vpn `
-VpnType RouteBased -GatewaySku VpnGw1
New-AzLocalNetworkGateway -Name $LNGName6 -ResourceGroupName $RG1 `
-Location $Location1 -GatewayIpAddress $LNGIP6 -AddressPrefix `
$LNGPrefix61,$LNGPrefix62
Step 2 - Create a site-to-site VPN connection with an IPsec/IKE policy
1. Create an IPsec/IKE policy
This sample script creates an IPsec/IKE policy with the following algorithms and parameters:
- IKEv2: AES128, SHA1, DHGroup14
- IPsec: AES256, SHA256, none, SA Lifetime 14400 seconds, and 102400000KB
$ipsecpolicy6 = New-AzIpsecPolicy -IkeEncryption AES128 -IkeIntegrity SHA1 -DhGroup DHGroup14 -IpsecEncryption AES256 -IpsecIntegrity SHA256 -PfsGroup none -SALifeTimeSeconds 14400 -SADataSizeKilobytes 102400000
If you use GCMAES for IPsec, you must use the same GCMAES algorithm and key length for both IPsec encryption and integrity.
2. Create the site-to-site VPN connection with the IPsec/IKE policy
Create a site-to-site VPN connection and apply the IPsec/IKE policy you created previously:
$vnet1gw = Get-AzVirtualNetworkGateway -Name $GWName1 -ResourceGroupName $RG1
$lng6 = Get-AzLocalNetworkGateway -Name $LNGName6 -ResourceGroupName $RG1
New-AzVirtualNetworkGatewayConnection -Name $Connection16 -ResourceGroupName $RG1 -VirtualNetworkGateway1 $vnet1gw -LocalNetworkGateway2 $lng6 -Location $Location1 -ConnectionType IPsec -IpsecPolicies $ipsecpolicy6 -SharedKey 'Azs123'
Important
Once an IPsec/IKE policy is specified on a connection, the Azure VPN gateway only sends or accepts the IPsec/IKE proposal with specified cryptographic algorithms and key strengths on that particular connection. Make sure your on-premises VPN device for the connection uses or accepts the exact policy combination, otherwise the site-to-site VPN tunnel cannot be established.
Part 4 - Update IPsec/IKE policy for a connection
The previous section showed how to manage IPsec/IKE policy for an existing site-to-site connection. This section walks through the following operations on a connection:
- Show the IPsec/IKE policy of a connection.
- Add or update the IPsec/IKE policy to a connection.
- Remove the IPsec/IKE policy from a connection.
Note
IPsec/IKE policy is supported on Standard and HighPerformance route-based VPN gateways only. It does not work on the Basic gateway SKU.
1. Show the IPsec/IKE policy of a connection
The following example shows how to get the IPsec/IKE policy configured on a connection. The scripts also continue from the previous exercises.
$RG1 = "TestPolicyRG1"
$Connection16 = "VNet1toSite6"
$connection6 = Get-AzVirtualNetworkGatewayConnection -Name $Connection16 -ResourceGroupName $RG1
$connection6.IpsecPolicies
The last command lists the current IPsec/IKE policy configured on the connection, if any. The following example is a sample output for the connection:
SALifeTimeSeconds : 14400
SADataSizeKilobytes : 102400000
IpsecEncryption : AES256
IpsecIntegrity : SHA256
IkeEncryption : AES128
IkeIntegrity : SHA1
DhGroup : DHGroup14
PfsGroup : None
If there's no IPsec/IKE policy configured, the command $connection6.policy gets an empty return. It does not mean that IPsec/IKE isn't configured on the connection; it means there's no custom IPsec/IKE policy. The actual connection uses the default policy negotiated between your on-premises VPN device and the Azure VPN gateway.
2. Add or update an IPsec/IKE policy for a connection
The steps to add a new policy or update an existing policy on a connection are the same: create a new policy, then apply the new policy to the connection:
$RG1 = "TestPolicyRG1"
$Connection16 = "VNet1toSite6"
$connection6 = Get-AzVirtualNetworkGatewayConnection -Name $Connection16 -ResourceGroupName $RG1
$newpolicy6 = New-AzIpsecPolicy -IkeEncryption AES128 -IkeIntegrity SHA1 -DhGroup DHGroup14 -IpsecEncryption AES256 -IpsecIntegrity SHA256 -PfsGroup None -SALifeTimeSeconds 14400 -SADataSizeKilobytes 102400000
$connection6.SharedKey = "AzS123"
Set-AzVirtualNetworkGatewayConnection -VirtualNetworkGatewayConnection $connection6 -IpsecPolicies $newpolicy6
You can get the connection again to check if the policy is updated:
$connection6 = Get-AzVirtualNetworkGatewayConnection -Name $Connection16 -ResourceGroupName $RG1
$connection6.IpsecPolicies
You should see the output from the last line, as shown in the following example:
SALifeTimeSeconds : 14400
SADataSizeKilobytes : 102400000
IpsecEncryption : AES256
IpsecIntegrity : SHA256
IkeEncryption : AES128
IkeIntegrity : SHA1
DhGroup : DHGroup14
PfsGroup : None
3. Remove an IPsec/IKE policy from a connection
After you remove the custom policy from a connection, the Azure VPN gateway reverts to the default IPsec/IKE proposal, and renegotiates with your on-premises VPN device.
$RG1 = "TestPolicyRG1"
$Connection16 = "VNet1toSite6"
$connection6 = Get-AzVirtualNetworkGatewayConnection -Name $Connection16 -ResourceGroupName $RG1
$connection6.SharedKey = "AzS123"
$currentpolicy = $connection6.IpsecPolicies[0]
$connection6.IpsecPolicies.Remove($currentpolicy)
Set-AzVirtualNetworkGatewayConnection -VirtualNetworkGatewayConnection $connection6
You can use the same script to check if the policy has been removed from the connection.
Next steps
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