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Step-by-Step Guide: How to Set Up IKEv2 VPN

Read this in other languages: English, 简体中文.

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

Introduction
Using helper scripts
Configure IKEv2 VPN clients
Manage client certificates
Manually set up IKEv2 on the VPN server
Known issues
Remove IKEv2
References

Introduction

Modern operating systems (such as Windows 7 and newer) 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 7, 8.x and 10
OS X (macOS)
Android 4.x and newer (using the strongSwan VPN client)
iOS (iPhone/iPad)

After following this guide, you will be able to connect to the VPN using IKEv2 in addition to the existing IPsec/L2TP and IPsec/XAuth ("Cisco IPsec") modes.

Using helper scripts

New: For macOS and iOS clients, the helper script can now create .mobileconfig files to simplify client setup and improve VPN performance.

Important: Before continuing, you should have successfully set up your own VPN server, and (optional but recommended) updated Libreswan. Docker users, see here.

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

wget https://git.io/ikev2setup -O ikev2.sh && sudo bash ikev2.sh --auto

The script must be run using bash, not sh. The command above runs the helper script in auto mode, using default options. Remove the --auto parameter if you want to customize IKEv2 setup options. When finished, continue to configure IKEv2 VPN clients.

Configure IKEv2 VPN clients

Read this in other languages: English, 简体中文.

Note: If you want to generate certificates for additional VPN clients, or export configuration for an existing client, just run the helper script again.

Windows 7, 8.x and 10
OS X (macOS)
iOS (iPhone/iPad)
Android

Windows 7, 8.x and 10

Securely transfer the generated .p12 file to your computer, then import it into the "Computer account" certificate store. Make sure that the client cert is placed in "Personal -> Certificates", and the CA cert is placed in "Trusted Root Certification Authorities -> Certificates".

Detailed instructions:
https://wiki.strongswan.org/projects/strongswan/wiki/Win7Certs

Note: Ubuntu 18.04 users may encounter the error "The password you entered is incorrect" when trying to import the generated .p12 file into Windows. See Known issues.
On the Windows computer, add a new IKEv2 VPN connection:
https://wiki.strongswan.org/projects/strongswan/wiki/Win7Config

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 Internet address field.
(Optional but recommended) 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.x and 10 (download .reg file)
```
REG ADD HKLM\SYSTEM\CurrentControlSet\Services\RasMan\Parameters /v NegotiateDH2048_AES256 /t REG_DWORD /d 0x1 /f
```
Start the new VPN connection, and enjoy your IKEv2 VPN!
https://wiki.strongswan.org/projects/strongswan/wiki/Win7Connect

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".

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. When finished, check to make sure "IKEv2 VPN configuration" is listed under System Preferences -> Profiles.

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

Open System Preferences and go to the Network section.
Click the + button in the lower-left corner of the window.
Select VPN from the Interface drop-down menu.
Select IKEv2 from the VPN Type drop-down menu.
Enter anything you like for the Service Name.
Click Create.
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.
Enter Your VPN Server IP (or DNS name) for the Remote ID.
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.
Click the Authentication Settings... button.
Select None from the Authentication Settings drop-down menu.
Select the Certificate radio button, then select the new client certificate.
Click OK.
Check the Show VPN status in menu bar checkbox.
Click Apply to save the VPN connection information.
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".

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:

AirDrop, or
Upload to your device using "File Sharing" in iTunes, 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 "Settings" to import, or
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 configuration" is listed under Settings -> General -> Profile(s).

Go to Settings -> General -> VPN.
Select the VPN connection with Your VPN Server IP (or DNS name).
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:

AirDrop, or
Upload to your device using "File Sharing" in iTunes, 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 "Settings" to import, or
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 -> Profiles.

Go to Settings -> General -> VPN.
Tap Add VPN Configuration....
Tap Type. Select IKEv2 and go back.
Tap Description and enter anything you like.
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.
Tap Remote ID and enter Your VPN Server IP (or DNS name).
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.
Tap User Authentication. Select None and go back.
Make sure the Use Certificate switch is ON.
Tap Certificate. Select the new client certificate and go back.
Tap Done.
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".

Android

Securely transfer the generated .sswan file to your Android device.
Install strongSwan VPN Client from Google Play.
Launch the strongSwan VPN client.
Tap the "more options" menu on top right, then tap Import VPN profile.
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.
On the "Import VPN profile" screen, tap IMPORT CERTIFICATE FROM VPN PROFILE, and follow the prompts.
On the "Choose certificate" screen, select the new client certificate, then tap Select.
Tap IMPORT.
Tap the new VPN profile to connect.

(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:

Securely transfer the generated .p12 file to your Android device.
Install strongSwan VPN Client from Google Play.
Launch the Settings application.
Go to Security -> Advanced -> Encryption & credentials.
Tap Install certificates from storage (or SD card).
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.
Launch the strongSwan VPN client and tap Add VPN Profile.
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.
Select IKEv2 Certificate from the VPN Type drop-down menu.
Tap Select user certificate, select the new client certificate and confirm.
(Important) Tap Show advanced settings. Scroll down, find and enable the Use RSA/PSS signatures option.
Save the new VPN connection, then tap to connect.

Android 4 to 9:

Securely transfer the generated .p12 file to your Android device.
Install strongSwan VPN Client from Google Play.
Launch the strongSwan VPN client and tap Add VPN Profile.
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.
Select IKEv2 Certificate from the VPN Type drop-down menu.
Tap Select user certificate, then tap Install certificate.
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.
(Important) Tap Show advanced settings. Scroll down, find and enable the Use RSA/PSS signatures option.
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".

Manage client certificates

Add a client certificate

If you want to generate certificates for additional IKEv2 VPN clients, just run the helper script again. Or you may 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 configuration for an existing client, run the helper script again and select the appropriate option.

Revoke a client certificate

In certain circumstances, you may need to revoke a previously generated VPN client certificate. This can be done using crlutil. See example steps below, commands must be run as root.

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.

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.

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:

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.

Finally, let Libreswan re-read the updated CRL.
```
ipsec crls
```

Manually set up IKEv2 on the VPN server

As an alternative to using the helper script, advanced users can manually set up IKEv2. The following example shows how to manually configure IKEv2 with Libreswan. Commands below must be run as root.

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.

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

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
  fragmentation=yes
  ike=aes256-sha2,aes128-sha2,aes256-sha1,aes128-sha1,aes256-sha2;modp1024,aes128-sha1;modp1024
  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

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 4096 -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 4096 -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...

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 simultaneously, 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 4096 -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).

(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

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.

(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.

Known issues

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.
Ubuntu 18.04 users may encounter the error "The password you entered is incorrect" when trying to import the generated .p12 file into Windows. This is due to a bug in NSS. Read more here.
Workaround for the NSS bug on Ubuntu 18.04

Note: This workaround should only be used on Ubuntu 18.04 systems running on the x86_64 architecture. As of 2021-01-21, the IKEv2 helper script was updated to automatically apply this workaround.

First, install newer versions of libnss3 related packages:
```
wget https://mirrors.kernel.org/ubuntu/pool/main/n/nss/libnss3_3.49.1-1ubuntu1.5_amd64.deb
wget https://mirrors.kernel.org/ubuntu/pool/main/n/nss/libnss3-dev_3.49.1-1ubuntu1.5_amd64.deb
wget https://mirrors.kernel.org/ubuntu/pool/universe/n/nss/libnss3-tools_3.49.1-1ubuntu1.5_amd64.deb
apt-get -y update
apt-get -y install "./libnss3_3.49.1-1ubuntu1.5_amd64.deb" \
  "./libnss3-dev_3.49.1-1ubuntu1.5_amd64.deb" \
  "./libnss3-tools_3.49.1-1ubuntu1.5_amd64.deb"
```
After that, export configuration for the IKEv2 client again.
If using the strongSwan Android VPN client, you must upgrade Libreswan on your server to version 3.26 or above.

Remove IKEv2

If you want to remove IKEv2 from the VPN server, but keep the IPsec/L2TP and IPsec/XAuth ("Cisco IPsec") modes, run the helper script again and select the "Remove IKEv2" option. Note that this will delete all IKEv2 configuration including certificates, and cannot be undone!

Alternatively, you can manually remove IKEv2. Click here for instructions.

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. Note that this will delete all IKEv2 configuration including certificates, and cannot be undone!

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.
(Important) Restart the IPsec service:
```
service ipsec restart
```

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

Delete certificates. Replace "Nickname" below with each certificate's nickname. Repeat for each certificate. When finished, list certificates in the IPsec database again, and confirm that the list is empty.
```
certutil -D -d sql:/etc/ipsec.d -n "Nickname"
```

29 KiB Raw Blame History

Step-by-Step Guide: How to Set Up IKEv2 VPN

Introduction

Using helper scripts

Configure IKEv2 VPN clients

Windows 7, 8.x and 10

OS X (macOS)

iOS

Android

Manage client certificates

Add a client certificate

Export configuration for an existing client

Revoke a client certificate

Manually set up IKEv2 on the VPN server

Known issues

Remove IKEv2

References

29 KiB

Raw Blame History