setup-ipsec-vpn/docs/ikev2-howto.md

Guide: How to Set Up and Use IKEv2 VPN

Read this in other languages: English, 中文.

Note: You may also connect using IPsec/L2TP or IPsec/XAuth mode.

• Introduction
• Configure IKEv2 VPN clients
• Manage client certificates
• Troubleshooting
• Change IKEv2 server address
• Update IKEv2 helper script
• Set up IKEv2 using helper script
• Manually set up IKEv2
• Remove IKEv2

Introduction

Modern operating systems support the IKEv2 standard. Internet Key Exchange (IKE or IKEv2) is the protocol used to set up a Security Association (SA) in the IPsec protocol suite. Compared to IKE version 1, IKEv2 contains improvements such as Standard Mobility support through MOBIKE, and improved reliability.

Libreswan can authenticate IKEv2 clients on the basis of X.509 Machine Certificates using RSA signatures. This method does not require an IPsec PSK, username or password. It can be used with Windows, macOS, iOS, Android, Linux and RouterOS.

By default, IKEv2 is automatically set up when running the VPN setup script. If you want to learn more about setting up IKEv2, see Set up IKEv2 using helper script. Docker users, see Configure and use IKEv2 VPN.

Configure IKEv2 VPN clients

Read this in other languages: English, 中文. Like this project? You can show your appreciation here.

Note: To add or export IKEv2 clients, run sudo ikev2.sh. Use -h to show usage. Client config files can be safely deleted after import.

• Windows 7, 8, 10 and 11
• OS X (macOS)
• iOS (iPhone/iPad)
• Android
• Linux
• Mikrotik RouterOS

Windows 7, 8, 10 and 11

Auto-import configuration

Windows 8, 10 and 11 users can automatically import IKEv2 configuration:

1. Securely transfer the generated .p12 file to your computer.
2. Right-click on ikev2_config_import.cmd and save this helper script to the same folder as the .p12 file.
3. Right-click on the saved script, select Properties. Click on Unblock at the bottom, then click on OK.
4. Right-click on the saved script, select Run as administrator and follow the prompts.

If you get an error when trying to connect, see Troubleshooting.

Manually import configuration

Alternatively, Windows 7, 8, 10 and 11 users can manually import IKEv2 configuration:

1. Securely transfer the generated .p12 file to your computer, then import it into the certificate store.

   To import the .p12 file, run the following from an elevated command prompt:

   # Import .p12 file (replace with your own value)
   certutil -f -importpfx "\path\to\your\file.p12" NoExport
   

   Note: If there is no password for client config files, press Enter to continue, or if manually importing the .p12 file, leave the password field blank.

   Alternatively, you can manually import the .p12 file. Make sure that the client cert is placed in "Personal -> Certificates", and the CA cert is placed in "Trusted Root Certification Authorities -> Certificates".

2. On the Windows computer, add a new IKEv2 VPN connection.

   For Windows 8, 10 and 11, it is recommended to create the VPN connection using the following commands from a command prompt, for improved security and performance.

   # Create VPN connection (replace server address with your own value)
   powershell -command "Add-VpnConnection -ServerAddress 'Your VPN Server IP (or DNS name)' -Name 'My IKEv2 VPN' -TunnelType IKEv2 -AuthenticationMethod MachineCertificate -EncryptionLevel Required -PassThru"
   # Set IPsec configuration
   powershell -command "Set-VpnConnectionIPsecConfiguration -ConnectionName 'My IKEv2 VPN' -AuthenticationTransformConstants GCMAES128 -CipherTransformConstants GCMAES128 -EncryptionMethod AES256 -IntegrityCheckMethod SHA256 -PfsGroup None -DHGroup Group14 -PassThru -Force"
   

   Windows 7 does not support these commands, you can manually create the VPN connection.

   Note: The server address you specify must exactly match the server address in the output of the IKEv2 helper script. For example, if you specified the server's DNS name during IKEv2 setup, you must enter the DNS name in the Internet address field.

3. This step is required if you manually created the VPN connection.

   Enable stronger ciphers for IKEv2 with a one-time registry change. Download and import the .reg file below, or run the following from an elevated command prompt. Read more here.

   • For Windows 7, 8, 10 and 11 (download .reg file)

     REG ADD HKLM\SYSTEM\CurrentControlSet\Services\RasMan\Parameters /v NegotiateDH2048_AES256 /t REG_DWORD /d 0x1 /f
     

To connect to the VPN: Click on the wireless/network icon in your system tray, select the new VPN entry, and click Connect. Once successfully connected, you can verify that your traffic is being routed properly by looking up your IP address on Google. It should say "Your public IP address is Your VPN Server IP".

If you get an error when trying to connect, see Troubleshooting.

Remove the IKEv2 VPN connection.

Using the following steps, you can remove the VPN connection and optionally restore the computer to the status before IKEv2 configuration import.

1. Remove the added VPN connection in Windows Settings - Network - VPN. Windows 7 users can remove the VPN connection in Network and Sharing Center - Change adapter settings.

2. (Optional) Remove IKEv2 certificates.

   1. Press Win+R, or search for mmc in the Start Menu. Open Microsoft Management Console.

   2. Open File - Add/Remove Snap-In. Select to add Certificates and in the window that opens, select Computer account -> Local Computer. Click on Finish -> OK to save the settings.

   3. Go to Certificates - Personal - Certificates and delete the IKEv2 client certificate. The name of the certificate is the same as the IKEv2 client name you specified (default: vpnclient). The certificate was issued by IKEv2 VPN CA.

   4. Go to Certificates - Trusted Root Certification Authorities - Certificates and delete the IKEv2 VPN CA certificate. The certificate was issued to IKEv2 VPN CA by IKEv2 VPN CA. Before deleting, make sure that there are no other certificate(s) issued by IKEv2 VPN CA in Certificates - Personal - Certificates.

3. (Optional. For users who manually created the VPN connection) Restore registry settings. Note that you should backup the registry before editing.

   1. Press Win+R, or search for regedit in the Start Menu. Open Registry Editor.

   2. Go to HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Rasman\Parameters and delete the item with name NegotiateDH2048_AES256, if it exists.

OS X (macOS)

First, securely transfer the generated .mobileconfig file to your Mac, then double-click and follow the prompts to import as a macOS profile. If your Mac runs macOS Big Sur or newer, open System Preferences and go to the Profiles section to finish importing. When finished, check to make sure "IKEv2 VPN" is listed under System Preferences -> Profiles.

To connect to the VPN:

1. Open System Preferences and go to the Network section.
2. Select the VPN connection with Your VPN Server IP (or DNS name).
3. Check the Show VPN status in menu bar checkbox.
4. Click Connect.

(Optional feature) You can choose to enable VPN On Demand. This is an "always-on" feature that can automatically connect to the VPN while on Wi-Fi. To enable, check the Connect on demand checkbox for the VPN connection, and click Apply.

If you manually set up IKEv2 without using the helper script, click here for instructions.

First, securely transfer the generated .p12 file to your Mac, then double-click to import into the login keychain in Keychain Access. Next, double-click on the imported IKEv2 VPN CA certificate, expand Trust and select Always Trust from the IP Security (IPsec) drop-down menu. Close the dialog using the red "X" on the top-left corner. When prompted, use Touch ID or enter your password and click "Update Settings".

When finished, check to make sure both the new client certificate and IKEv2 VPN CA are listed under the Certificates category of login keychain.

1. Open System Preferences and go to the Network section.
2. Click the + button in the lower-left corner of the window.
3. Select VPN from the Interface drop-down menu.
4. Select IKEv2 from the VPN Type drop-down menu.
5. Enter anything you like for the Service Name.
6. Click Create.
7. Enter Your VPN Server IP (or DNS name) for the Server Address.
   Note: If you specified the server's DNS name (instead of its IP address) during IKEv2 setup, you must enter the DNS name in the Server Address and Remote ID fields.
8. Enter Your VPN Server IP (or DNS name) for the Remote ID.
9. Enter Your VPN client name in the Local ID field.
   Note: This must match exactly the client name you specified during IKEv2 setup. Same as the first part of your .p12 filename.
10. Click the Authentication Settings... button.
11. Select None from the Authentication Settings drop-down menu.
12. Select the Certificate radio button, then select the new client certificate.
13. Click OK.
14. Check the Show VPN status in menu bar checkbox.
15. Click Apply to save the VPN connection information.
16. Click Connect.

Once successfully connected, you can verify that your traffic is being routed properly by looking up your IP address on Google. It should say "Your public IP address is Your VPN Server IP".

If you get an error when trying to connect, see Troubleshooting.

Remove the IKEv2 VPN connection.

To remove the IKEv2 VPN connection, open System Preferences -> Profiles and remove the IKEv2 VPN profile you added.

iOS

First, securely transfer the generated .mobileconfig file to your iOS device, then import it as an iOS profile. To transfer the file, you may use:

1. AirDrop, or
2. Upload to your device (any App folder) using File Sharing, then open the "Files" App on your iOS device, move the uploaded file to the "On My iPhone" folder. After that, tap the file and go to the "Settings" App to import, or
3. Host the file on a secure website of yours, then download and import it in Mobile Safari.

When finished, check to make sure "IKEv2 VPN" is listed under Settings -> General -> VPN & Device Management or Profile(s).

To connect to the VPN:

1. Go to Settings -> VPN. Select the VPN connection with Your VPN Server IP (or DNS name).
2. Slide the VPN switch ON.

(Optional feature) You can choose to enable VPN On Demand. This is an "always-on" feature that can automatically connect to the VPN while on Wi-Fi. To enable, tap the "i" icon on the right of the VPN connection, and enable Connect On Demand.

If you manually set up IKEv2 without using the helper script, click here for instructions.

First, securely transfer the generated ikev2vpnca.cer and .p12 files to your iOS device, then import them one by one as iOS profiles. To transfer the files, you may use:

1. AirDrop, or
2. Upload to your device (any App folder) using File Sharing, then open the "Files" App on your iOS device, move the uploaded files to the "On My iPhone" folder. After that, tap each file and go to the "Settings" App to import, or
3. Host the files on a secure website of yours, then download and import them in Mobile Safari.

When finished, check to make sure both the new client certificate and IKEv2 VPN CA are listed under Settings -> General -> VPN & Device Management or Profile(s).

1. Go to Settings -> General -> VPN & Device Management -> VPN.
2. Tap Add VPN Configuration....
3. Tap Type. Select IKEv2 and go back.
4. Tap Description and enter anything you like.
5. Tap Server and enter Your VPN Server IP (or DNS name).
   Note: If you specified the server's DNS name (instead of its IP address) during IKEv2 setup, you must enter the DNS name in the Server and Remote ID fields.
6. Tap Remote ID and enter Your VPN Server IP (or DNS name).
7. Enter Your VPN client name in the Local ID field.
   Note: This must match exactly the client name you specified during IKEv2 setup. Same as the first part of your .p12 filename.
8. Tap User Authentication. Select None and go back.
9. Make sure the Use Certificate switch is ON.
10. Tap Certificate. Select the new client certificate and go back.
11. Tap Done.
12. Slide the VPN switch ON.

Once successfully connected, you can verify that your traffic is being routed properly by looking up your IP address on Google. It should say "Your public IP address is Your VPN Server IP".

If you get an error when trying to connect, see Troubleshooting.

Remove the IKEv2 VPN connection.

To remove the IKEv2 VPN connection, open Settings -> General -> VPN & Device Management or Profile(s) and remove the IKEv2 VPN profile you added.

Android

1. Securely transfer the generated .sswan file to your Android device.
2. Install strongSwan VPN Client from Google Play, F-Droid or strongSwan download server.
3. Launch the strongSwan VPN client.
4. Tap the "more options" menu on top right, then tap Import VPN profile.
5. Choose the .sswan file you transferred from the VPN server.
   Note: To find the .sswan file, tap the three-line menu button, then browse to the location you saved the file.
6. On the "Import VPN profile" screen, tap IMPORT CERTIFICATE FROM VPN PROFILE, and follow the prompts.
7. On the "Choose certificate" screen, select the new client certificate, then tap Select.
8. Tap IMPORT.
9. Tap the new VPN profile to connect.

If your device runs Android 6.0 or older, click here for additional instructions.

If your device runs Android 6.0 (Marshmallow) or older, in order to connect using the strongSwan VPN client, you must make the following change on the VPN server: Edit /etc/ipsec.d/ikev2.conf on the server. Append authby=rsa-sha1 to the end of the conn ikev2-cp section, indented by two spaces. Save the file and run service ipsec restart.

(Optional feature) You can choose to enable the "Always-on VPN" feature on Android. Launch the Settings app, go to Network & internet -> Advanced -> VPN, click the gear icon on the right of "strongSwan VPN Client", then enable the Always-on VPN and Block connections without VPN options.

If you manually set up IKEv2 without using the helper script, click here for instructions.

Android 10 and newer:

1. Securely transfer the generated .p12 file to your Android device.
2. Install strongSwan VPN Client from Google Play, F-Droid or strongSwan download server.
3. Launch the Settings application.
4. Go to Security -> Advanced -> Encryption & credentials.
5. Tap Install certificates from storage (or SD card).
6. Choose the .p12 file you transferred from the VPN server, and follow the prompts.
   Note: To find the .p12 file, tap the three-line menu button, then browse to the location you saved the file.
7. Launch the strongSwan VPN client and tap Add VPN Profile.
8. Enter Your VPN Server IP (or DNS name) in the Server field.
   Note: If you specified the server's DNS name (instead of its IP address) during IKEv2 setup, you must enter the DNS name in the Server field.
9. Select IKEv2 Certificate from the VPN Type drop-down menu.
10. Tap Select user certificate, select the new client certificate and confirm.
11. (Important) Tap Show advanced settings. Scroll down, find and enable the Use RSA/PSS signatures option.
12. Save the new VPN connection, then tap to connect.

Android 4 to 9:

1. Securely transfer the generated .p12 file to your Android device.
2. Install strongSwan VPN Client from Google Play, F-Droid or strongSwan download server.
3. Launch the strongSwan VPN client and tap Add VPN Profile.
4. Enter Your VPN Server IP (or DNS name) in the Server field.
   Note: If you specified the server's DNS name (instead of its IP address) during IKEv2 setup, you must enter the DNS name in the Server field.
5. Select IKEv2 Certificate from the VPN Type drop-down menu.
6. Tap Select user certificate, then tap Install certificate.
7. Choose the .p12 file you transferred from the VPN server, and follow the prompts.
   Note: To find the .p12 file, tap the three-line menu button, then browse to the location you saved the file.
8. (Important) Tap Show advanced settings. Scroll down, find and enable the Use RSA/PSS signatures option.
9. Save the new VPN connection, then tap to connect.

Once successfully connected, you can verify that your traffic is being routed properly by looking up your IP address on Google. It should say "Your public IP address is Your VPN Server IP".

If you get an error when trying to connect, see Troubleshooting.

Linux

Before configuring Linux VPN clients, you must make the following change on the VPN server: Edit /etc/ipsec.d/ikev2.conf on the server. Append authby=rsa-sha1 to the end of the conn ikev2-cp section, indented by two spaces. Save the file and run service ipsec restart.

To configure your Linux computer to connect to IKEv2 as a VPN client, first install the strongSwan plugin for NetworkManager:

# Ubuntu and Debian
sudo apt-get update
sudo apt-get install network-manager-strongswan

# Arch Linux
sudo pacman -Syu  # upgrade all packages
sudo pacman -S networkmanager-strongswan

# Fedora
sudo yum install NetworkManager-strongswan-gnome

# CentOS
sudo yum install epel-release
sudo yum --enablerepo=epel install NetworkManager-strongswan-gnome

Next, securely transfer the generated .p12 file from the VPN server to your Linux computer. After that, extract the CA certificate, client certificate and private key. Replace vpnclient.p12 in the example below with the name of your .p12 file.

# Example: Extract CA certificate, client certificate and private key.
#          You may delete the .p12 file when finished.
# Note: You may need to enter the import password, which can be found
#       in the output of the IKEv2 helper script. If the output does not
#       contain an import password, press Enter to continue.
openssl pkcs12 -in vpnclient.p12 -cacerts -nokeys -out ikev2vpnca.cer
openssl pkcs12 -in vpnclient.p12 -clcerts -nokeys -out vpnclient.cer
openssl pkcs12 -in vpnclient.p12 -nocerts -nodes  -out vpnclient.key
rm vpnclient.p12

# (Important) Protect certificate and private key files
# Note: This step is optional, but strongly recommended.
sudo chown root.root ikev2vpnca.cer vpnclient.cer vpnclient.key
sudo chmod 600 ikev2vpnca.cer vpnclient.cer vpnclient.key

You can then set up and enable the VPN connection:

1. Go to Settings -> Network -> VPN. Click the + button.
2. Select IPsec/IKEv2 (strongswan).
3. Enter anything you like in the Name field.
4. In the Gateway (Server) section, enter Your VPN Server IP (or DNS name) for the Address.
5. Select the ikev2vpnca.cer file for the Certificate.
6. In the Client section, select Certificate(/private key) in the Authentication drop-down menu.
7. Select Certificate/private key in the Certificate drop-down menu (if exists).
8. Select the vpnclient.cer file for the Certificate (file).
9. Select the vpnclient.key file for the Private key.
10. In the Options section, check the Request an inner IP address checkbox.
11. In the Cipher proposals (Algorithms) section, check the Enable custom proposals checkbox.
12. Leave the IKE field blank.
13. Enter aes128gcm16 in the ESP field.
14. Click Add to save the VPN connection information.
15. Turn the VPN switch ON.

Once successfully connected, you can verify that your traffic is being routed properly by looking up your IP address on Google. It should say "Your public IP address is Your VPN Server IP".

If you get an error when trying to connect, see Troubleshooting.

RouterOS

Note: These steps were contributed by @Unix-User.

1. Securely transfer the generated .p12 file to your computer.

   Click to see screencast.

   

2. In WinBox, go to System > certificates > import. Import the .p12 certificate file twice (yes, import the same file two times!). Verify in your certificates panel. You will see 2 files, the one that is marked KT is the key.

   Click to see screencast.

   

3. Run these commands in terminal. Replace the following with your own values. YOUR_VPN_SERVER_IP_OR_DNS_NAME is your VPN server IP or DNS name. IMPORTED_CERTIFICATE is the name of the certificate from step 2 above, e.g. vpnclient.p12_0 (the one flagged with KT - Priv. Key Trusted - if not flagged as KT, import certificate again). THESE_ADDRESSES_GO_THROUGH_VPN are the local network addresses that you want to browse through the VPN. Assuming that your local network behind RouterOS is 192.168.0.0/24, you can use 192.168.0.0/24 for the entire network, or use 192.168.0.10 for just one device, and so on.

   /ip firewall address-list
   add address=THESE_ADDRESSES_GO_THROUGH_VPN list=local
   /ip ipsec mode-config
   add name=ike2-rw responder=no src-address-list=local
   /ip ipsec policy group
   add name=ike2-rw
   /ip ipsec profile
   add name=ike2-rw
   /ip ipsec peer
   add address=YOUR_VPN_SERVER_IP_OR_DNS_NAME exchange-mode=ike2 name=ike2-rw-client profile=ike2-rw
   /ip ipsec proposal
   add name=ike2-rw pfs-group=none
   /ip ipsec identity
   add auth-method=digital-signature certificate=IMPORTED_CERTIFICATE generate-policy=port-strict mode-config=ike2-rw \
       peer=ike2-rw-client policy-template-group=ike2-rw
   /ip ipsec policy
   add group=ike2-rw proposal=ike2-rw template=yes
   

4. For more information, see #1112.

tested on
mar/02/2022 12:52:57 by RouterOS 6.48
RouterBOARD 941-2nD

Manage client certificates

• List existing clients
• Add a client certificate
• Export configuration for an existing client
• Delete a client certificate
• Revoke a client certificate

List existing clients

To list the names of existing IKEv2 clients, run the helper script with the --listclients option. Use option -h to show usage.

sudo ikev2.sh --listclients

Add a client certificate

To add certificates for additional IKEv2 clients, run the helper script with the --addclient option. To customize client options, run the script without arguments.

sudo ikev2.sh --addclient [client name]

Alternatively, you may manually add a client certificate. Refer to step 4 in this section.

Export configuration for an existing client

By default, the IKEv2 helper script exports client configuration after running. If later you want to export an existing client, you may use:

sudo ikev2.sh --exportclient [client name]

Delete a client certificate

Important: Deleting a client certificate from the IPsec database WILL NOT prevent VPN client(s) from connecting using that certificate! For this use case, you MUST revoke the client certificate instead of deleting it.

First, read the important note above. Then click here for instructions.

Warning: The client certificate and private key will be permanently deleted. This cannot be undone!

To delete a client certificate:

sudo ikev2.sh --deleteclient [client name]

Alternatively, you can manually delete a client certificate.

1. List certificates in the IPsec database:

   certutil -L -d sql:/etc/ipsec.d
   

   Example output:

   Certificate Nickname                               Trust Attributes
                                                      SSL,S/MIME,JAR/XPI
   
   IKEv2 VPN CA                                       CTu,u,u
   ($PUBLIC_IP)                                       u,u,u
   vpnclient                                          u,u,u
   

2. Delete the client certificate and private key. Replace "Nickname" below with the nickname of the client certificate you want to delete, e.g. vpnclient.

   certutil -F -d sql:/etc/ipsec.d -n "Nickname"
   certutil -D -d sql:/etc/ipsec.d -n "Nickname" 2>/dev/null
   

3. (Optional) Delete the previously generated client configuration files (.p12, .mobileconfig and .sswan files) for this VPN client, if any.

Revoke a client certificate

In certain circumstances, you may need to revoke a previously generated VPN client certificate. To revoke a certificate, run the helper script.

sudo ikev2.sh --revokeclient [client name]

Alternatively, you can manually revoke a client certificate.

Alternatively, you can manually revoke a client certificate. This can be done using crlutil. See example steps below, commands must be run as root.

1. Check the database, and identify the nickname of the client certificate you want to revoke.

   certutil -L -d sql:/etc/ipsec.d
   

   Certificate Nickname                               Trust Attributes
                                                      SSL,S/MIME,JAR/XPI
   
   IKEv2 VPN CA                                       CTu,u,u
   ($PUBLIC_IP)                                       u,u,u
   vpnclient-to-revoke                                u,u,u
   

   In this example, we will revoke the certificate with nickname vpnclient-to-revoke, issued by IKEv2 VPN CA.

2. Find the serial number of this client certificate.

   certutil -L -d sql:/etc/ipsec.d -n "vpnclient-to-revoke"
   

   Certificate:
       Data:
           Version: 3 (0x2)
           Serial Number:
               00:cd:69:ff:74
   ... ...
   

   From the output, we see that the serial number is CD69FF74 in hexadecimal, which is 3446275956 in decimal. It will be used in the next steps.

3. Create a new Certificate Revocation List (CRL). You only need to do this once for each CA.

   if ! crlutil -L -d sql:/etc/ipsec.d -n "IKEv2 VPN CA" 2>/dev/null; then
     crlutil -G -d sql:/etc/ipsec.d -n "IKEv2 VPN CA" -c /dev/null
   fi
   

   CRL Info:
   :
       Version: 2 (0x1)
       Signature Algorithm: PKCS #1 SHA-256 With RSA Encryption
       Issuer: "O=IKEv2 VPN,CN=IKEv2 VPN CA"
       This Update: Sat Jun 06 22:00:00 2020
       CRL Extensions:
   

4. Add the client certificate you want to revoke to the CRL. Here we specify the certificate's serial number in decimal, and the revocation time in GeneralizedTime format (YYYYMMDDhhmmssZ) in UTC.

   crlutil -M -d sql:/etc/ipsec.d -n "IKEv2 VPN CA" <<EOF
   addcert 3446275956 20200606220100Z
   EOF
   

   CRL Info:
   :
       Version: 2 (0x1)
       Signature Algorithm: PKCS #1 SHA-256 With RSA Encryption
       Issuer: "O=IKEv2 VPN,CN=IKEv2 VPN CA"
       This Update: Sat Jun 06 22:02:00 2020
       Entry 1 (0x1):
           Serial Number:
               00:cd:69:ff:74
           Revocation Date: Sat Jun 06 22:01:00 2020
       CRL Extensions:
   

   Note: If you want to remove a certificate from the CRL, replace addcert 3446275956 20200606220100Z above with rmcert 3446275956. For other crlutil usage, read here.

5. Finally, let Libreswan re-read the updated CRL.

   ipsec crls
   

Troubleshooting

Read this in other languages: English, 中文.

See also: Check logs and VPN status, IKEv1 troubleshooting and Advanced usage.

• Cannot open websites after connecting to IKEv2
• IKE authentication credentials are unacceptable
• Policy match error
• IKEv2 disconnects after one hour
• Unable to connect multiple IKEv2 clients
• Other known issues

Cannot open websites after connecting to IKEv2

If your VPN client device cannot open websites after successfully connecting to IKEv2, try the following fixes:

1. Some cloud providers, such as Google Cloud, set a lower MTU by default. This could cause network issues with IKEv2 VPN clients. To fix, try setting the MTU to 1500 on the VPN server:

   # Replace ens4 with the network interface name on your server
   sudo ifconfig ens4 mtu 1500
   

   This setting does not persist after a reboot. To change the MTU size permanently, refer to relevant articles on the web.

2. If changing the MTU size does not fix the issue, try the fix in Android MTU/MSS issues.

3. In certain circumstances, Windows does not use the DNS servers specified by IKEv2 after connecting. This can be fixed by manually entering DNS servers such as Google Public DNS (8.8.8.8, 8.8.4.4) in network interface properties -> TCP/IPv4.

IKE authentication credentials are unacceptable

If you encounter this error, make sure that the VPN server address specified on your VPN client device exactly matches the server address in the output of the IKEv2 helper script. For example, you cannot use a DNS name to connect if it was not specified when setting up IKEv2. To change the IKEv2 server address, read this section.

Policy match error

To fix this error, you will need to enable stronger ciphers for IKEv2 with a one-time registry change. Download and import the .reg file below, or run the following from an elevated command prompt.

• For Windows 7, 8, 10 and 11 (download .reg file)

REG ADD HKLM\SYSTEM\CurrentControlSet\Services\RasMan\Parameters /v NegotiateDH2048_AES256 /t REG_DWORD /d 0x1 /f

IKEv2 disconnects after one hour

If the IKEv2 connection disconnects automatically after one hour (60 minutes), apply this fix: Edit /etc/ipsec.d/ikev2.conf on the VPN server (or /etc/ipsec.conf if it does not exist), append these lines to the end of section conn ikev2-cp, indented by two spaces:

  ikelifetime=24h
  salifetime=24h

Save the file and run service ipsec restart. As of 2021-01-20, the IKEv2 helper script was updated to include this fix.

Unable to connect multiple IKEv2 clients

To connect multiple IKEv2 clients, you must generate a unique certificate for each.

If you are unable to connect multiple IKEv2 clients from behind the same NAT (e.g. home router), apply this fix: Edit /etc/ipsec.d/ikev2.conf on the VPN server, find the line leftid=@<your_server_ip> and remove the @, i.e. replace it with leftid=<your_server_ip>. Save the file and run service ipsec restart. Do not apply this fix if leftid is a DNS name, which is not affected. As of 2021-02-01, the IKEv2 helper script was updated to include this fix.

Other known issues

1. The built-in VPN client in Windows may not support IKEv2 fragmentation (this feature requires Windows 10 v1803 or newer). On some networks, this can cause the connection to fail or have other issues. You may instead try the IPsec/L2TP or IPsec/XAuth mode.
2. If using the strongSwan Android VPN client, you must update Libreswan on your server to version 3.26 or above.

Change IKEv2 server address

In certain circumstances, you may need to change the IKEv2 server address after setup. For example, to switch to use a DNS name, or after server IP changes. Note that the server address you specify on VPN client devices must exactly match the server address in the output of the IKEv2 helper script. Otherwise, devices may be unable to connect.

To change the server address, run the helper script and follow the prompts.

wget https://get.vpnsetup.net/ikev2addr -O ikev2addr.sh
sudo bash ikev2addr.sh

Important: After running this script, you must manually update the server address (and remote ID, if applicable) on any existing IKEv2 client devices. For iOS clients, you'll need to export and re-import client configuration using the IKEv2 helper script.

Update IKEv2 helper script

The IKEv2 helper script is updated from time to time for bug fixes and improvements (commit log). When a newer version is available, you may optionally update the IKEv2 helper script on your server. Note that these commands will overwrite any existing ikev2.sh.

wget https://get.vpnsetup.net/ikev2 -O /opt/src/ikev2.sh
chmod +x /opt/src/ikev2.sh && ln -s /opt/src/ikev2.sh /usr/bin 2>/dev/null

Set up IKEv2 using helper script

Note: By default, IKEv2 is automatically set up when running the VPN setup script. You may skip this section and continue to configure IKEv2 VPN clients.

Important: Before continuing, you should have successfully set up your own VPN server. Docker users, see here.

Use this helper script to automatically set up IKEv2 on the VPN server:

# Set up IKEv2 using default options
sudo ikev2.sh --auto
# Alternatively, you may customize IKEv2 options
sudo ikev2.sh

Note: If IKEv2 is already set up, but you want to customize IKEv2 options, first remove IKEv2, then set it up again using sudo ikev2.sh.

When finished, continue to configure IKEv2 VPN clients. Advanced users can optionally enable IKEv2-only mode.

Error: "sudo: ikev2.sh: command not found".

This is normal if you used an older version of the VPN setup script. First, download the IKEv2 helper script:

wget https://get.vpnsetup.net/ikev2 -O /opt/src/ikev2.sh
chmod +x /opt/src/ikev2.sh && ln -s /opt/src/ikev2.sh /usr/bin

Then run the script using the instructions above.

You may optionally specify a DNS name, client name and/or custom DNS servers.

When running IKEv2 setup in auto mode, advanced users can optionally specify a DNS name for the IKEv2 server address. The DNS name must be a fully qualified domain name (FQDN). Example:

sudo VPN_DNS_NAME='vpn.example.com' ikev2.sh --auto

Similarly, you may specify a name for the first IKEv2 client. The default is vpnclient if not specified.

sudo VPN_CLIENT_NAME='your_client_name' ikev2.sh --auto

By default, IKEv2 clients are set to use Google Public DNS when the VPN is active. You may specify custom DNS server(s) for IKEv2. Example:

sudo VPN_DNS_SRV1=1.1.1.1 VPN_DNS_SRV2=1.0.0.1 ikev2.sh --auto

By default, no password is required when importing IKEv2 client configuration. You can choose to protect client config files using a random password.

sudo VPN_PROTECT_CONFIG=yes ikev2.sh --auto

Learn how to change the IKEv2 server address.

In certain circumstances, you may need to change the IKEv2 server address after setup. For example, to switch to use a DNS name, or after server IP changes. Learn more in this section.

View usage information for the IKEv2 script.

Usage: bash ikev2.sh [options]

Options:
  --auto                        run IKEv2 setup in auto mode using default options (for initial setup only)
  --addclient [client name]     add a new client using default options
  --exportclient [client name]  export configuration for an existing client
  --listclients                 list the names of existing clients
  --revokeclient [client name]  revoke a client certificate
  --deleteclient [client name]  delete a client certificate
  --removeikev2                 remove IKEv2 and delete all certificates and keys from the IPsec database
  -h, --help                    show this help message and exit

To customize IKEv2 or client options, run this script without arguments.

Manually set up IKEv2

As an alternative to using the helper script, advanced users can manually set up IKEv2 on the VPN server. Before continuing, it is recommended to update Libreswan to the latest version.

The following example shows how to manually configure IKEv2 with Libreswan. Commands below must be run as root.

View example steps for manually configuring IKEv2 with Libreswan.

1. Find the VPN server's public IP, save it to a variable and check.

   PUBLIC_IP=$(dig @resolver1.opendns.com -t A -4 myip.opendns.com +short)
   [ -z "$PUBLIC_IP" ] && PUBLIC_IP=$(wget -t 3 -T 15 -qO- http://ipv4.icanhazip.com)
   printf '%s\n' "$PUBLIC_IP"
   

   Check to make sure the output matches the server's public IP. This variable is required in the steps below.

   Note: Alternatively, you may specify the server's DNS name here. e.g. PUBLIC_IP=myvpn.example.com.

2. Add a new IKEv2 connection:

   if ! grep -qs '^include /etc/ipsec\.d/\*\.conf$' /etc/ipsec.conf; then
     echo >> /etc/ipsec.conf
     echo 'include /etc/ipsec.d/*.conf' >> /etc/ipsec.conf
   fi
   

   Note: If you specified the server's DNS name (instead of its IP address) in step 1 above, you must replace leftid=$PUBLIC_IP in the command below with leftid=@$PUBLIC_IP.

   cat > /etc/ipsec.d/ikev2.conf <<EOF
   
   conn ikev2-cp
     left=%defaultroute
     leftcert=$PUBLIC_IP
     leftid=$PUBLIC_IP
     leftsendcert=always
     leftsubnet=0.0.0.0/0
     leftrsasigkey=%cert
     right=%any
     rightid=%fromcert
     rightaddresspool=192.168.43.10-192.168.43.250
     rightca=%same
     rightrsasigkey=%cert
     narrowing=yes
     dpddelay=30
     dpdtimeout=120
     dpdaction=clear
     auto=add
     ikev2=insist
     rekey=no
     pfs=no
     ike=aes256-sha2,aes128-sha2,aes256-sha1,aes128-sha1
     phase2alg=aes_gcm-null,aes128-sha1,aes256-sha1,aes128-sha2,aes256-sha2
     ikelifetime=24h
     salifetime=24h
   EOF
   

   We need to add a few more lines to that file. First check your Libreswan version, then run one of the following commands:

   ipsec --version
   

   For Libreswan 3.23 and newer:

   cat >> /etc/ipsec.d/ikev2.conf <<EOF
     modecfgdns="8.8.8.8 8.8.4.4"
     encapsulation=yes
     mobike=no
   EOF
   

   Note: The MOBIKE IKEv2 extension allows VPN clients to change network attachment points, e.g. switch between mobile data and Wi-Fi and keep the IPsec tunnel up on the new IP. If your server (or Docker host) is NOT running Ubuntu Linux, and you wish to enable MOBIKE support, replace mobike=no with mobike=yes in the command above. DO NOT enable this option on Ubuntu systems or Raspberry Pis.

   For Libreswan 3.19-3.22:

   cat >> /etc/ipsec.d/ikev2.conf <<EOF
     modecfgdns1=8.8.8.8
     modecfgdns2=8.8.4.4
     encapsulation=yes
   EOF
   

   For Libreswan 3.18 and older:

   cat >> /etc/ipsec.d/ikev2.conf <<EOF
     modecfgdns1=8.8.8.8
     modecfgdns2=8.8.4.4
     forceencaps=yes
   EOF
   

3. Generate Certificate Authority (CA) and VPN server certificates.

   Note: Specify the certificate validity period (in months) with "-v". e.g. "-v 120".

   Generate CA certificate:

   certutil -z <(head -c 1024 /dev/urandom) \
     -S -x -n "IKEv2 VPN CA" \
     -s "O=IKEv2 VPN,CN=IKEv2 VPN CA" \
     -k rsa -g 3072 -v 120 \
     -d sql:/etc/ipsec.d -t "CT,," -2
   

   Generating key.  This may take a few moments...
   
   Is this a CA certificate [y/N]?
   y
   Enter the path length constraint, enter to skip [<0 for unlimited path]: >
   Is this a critical extension [y/N]?
   N
   

   Generate VPN server certificate:

   Note: If you specified the server's DNS name (instead of its IP address) in step 1 above, you must replace --extSAN "ip:$PUBLIC_IP,dns:$PUBLIC_IP" in the command below with --extSAN "dns:$PUBLIC_IP".

   certutil -z <(head -c 1024 /dev/urandom) \
     -S -c "IKEv2 VPN CA" -n "$PUBLIC_IP" \
     -s "O=IKEv2 VPN,CN=$PUBLIC_IP" \
     -k rsa -g 3072 -v 120 \
     -d sql:/etc/ipsec.d -t ",," \
     --keyUsage digitalSignature,keyEncipherment \
     --extKeyUsage serverAuth \
     --extSAN "ip:$PUBLIC_IP,dns:$PUBLIC_IP"
   

   Generating key.  This may take a few moments...
   

4. Generate client certificate(s), then export the .p12 file that contains the client certificate, private key, and CA certificate.

   Note: You may repeat this step to generate certificates for additional VPN clients, but make sure to replace every vpnclient with vpnclient2, etc. To connect multiple VPN clients, you must generate a unique certificate for each.

   Generate client certificate:

   certutil -z <(head -c 1024 /dev/urandom) \
     -S -c "IKEv2 VPN CA" -n "vpnclient" \
     -s "O=IKEv2 VPN,CN=vpnclient" \
     -k rsa -g 3072 -v 120 \
     -d sql:/etc/ipsec.d -t ",," \
     --keyUsage digitalSignature,keyEncipherment \
     --extKeyUsage serverAuth,clientAuth -8 "vpnclient"
   

   Generating key.  This may take a few moments...
   

   Export .p12 file:

   pk12util -d sql:/etc/ipsec.d -n "vpnclient" -o vpnclient.p12
   

   Enter password for PKCS12 file:
   Re-enter password:
   pk12util: PKCS12 EXPORT SUCCESSFUL
   

   Enter a secure password to protect the exported .p12 file (when importing into an iOS or macOS device, this password cannot be empty).

5. (For iOS clients) Export the CA certificate as ikev2vpnca.cer:

   certutil -L -d sql:/etc/ipsec.d -n "IKEv2 VPN CA" -a -o ikev2vpnca.cer
   

6. The database should now contain:

   certutil -L -d sql:/etc/ipsec.d
   

   Certificate Nickname                               Trust Attributes
                                                      SSL,S/MIME,JAR/XPI
   
   IKEv2 VPN CA                                       CTu,u,u
   ($PUBLIC_IP)                                       u,u,u
   vpnclient                                          u,u,u
   

   Note: To display a certificate, use certutil -L -d sql:/etc/ipsec.d -n "Nickname". To revoke a client certificate, follow these steps. For other certutil usage, read here.

7. (Important) Restart the IPsec service:

   service ipsec restart
   

Before continuing, you must restart the IPsec service. The IKEv2 setup on the VPN server is now complete. Follow instructions to configure VPN clients.

Remove IKEv2

If you want to remove IKEv2 from the VPN server, but keep the IPsec/L2TP and IPsec/XAuth ("Cisco IPsec") modes (if installed), run the helper script. Warning: All IKEv2 configuration including certificates and keys will be permanently deleted. This cannot be undone!

sudo ikev2.sh --removeikev2

After removing IKEv2, if you want to set it up again, refer to this section.

Alternatively, you can manually remove IKEv2.

To manually remove IKEv2 from the VPN server, but keep the IPsec/L2TP and IPsec/XAuth ("Cisco IPsec") modes, follow these steps. Commands must be run as root.

Warning: All IKEv2 configuration including certificates and keys will be permanently deleted. This cannot be undone!

1. Rename (or delete) the IKEv2 config file:

   mv /etc/ipsec.d/ikev2.conf /etc/ipsec.d/ikev2.conf.bak
   

   Note: If you used an older version (before 2020-05-31) of the IKEv2 helper script or instructions, file /etc/ipsec.d/ikev2.conf may not exist. In this case, please instead remove the conn ikev2-cp section from file /etc/ipsec.conf.

2. (Important) Restart the IPsec service:

   service ipsec restart
   

3. List certificates in the IPsec database:

   certutil -L -d sql:/etc/ipsec.d
   

   Example output:

   Certificate Nickname                               Trust Attributes
                                                      SSL,S/MIME,JAR/XPI
   
   IKEv2 VPN CA                                       CTu,u,u
   ($PUBLIC_IP)                                       u,u,u
   vpnclient                                          u,u,u
   

4. Delete the Certificate Revocation List (CRL), if any:

   crlutil -D -d sql:/etc/ipsec.d -n "IKEv2 VPN CA" 2>/dev/null
   

5. Delete certificates and keys. Replace "Nickname" below with each certificate's nickname. Repeat these commands for each certificate. When finished, list certificates in the IPsec database again, and confirm that the list is empty.

   certutil -F -d sql:/etc/ipsec.d -n "Nickname"
   certutil -D -d sql:/etc/ipsec.d -n "Nickname" 2>/dev/null
   

References

• https://libreswan.org/wiki/VPN_server_for_remote_clients_using_IKEv2
• https://libreswan.org/wiki/HOWTO:_Using_NSS_with_libreswan
• https://libreswan.org/man/ipsec.conf.5.html
• https://wiki.strongswan.org/projects/strongswan/wiki/WindowsClients
• https://wiki.strongswan.org/projects/strongswan/wiki/AndroidVpnClient
• https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/tools/NSS_Tools_certutil
• https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/tools/NSS_Tools_crlutil

License

Copyright (C) 2016-2022 Lin Song

This work is licensed under the Creative Commons Attribution-ShareAlike 3.0 Unported License
Attribution required: please include my name in any derivative and let me know how you have improved it!