chromium/chromeos/components/test/data/onc/policy/policy_vpn_ipsec.onc

{
  "NetworkConfigurations": [
    {
      "GUID": "{a3860e83-f03d-4cb1-bafa-b22c9e746950}",
      "Name": "my vpn",
      "Type": "VPN",
      "VPN": {
        "AutoConnect": false,
        "Host": "vpn.my.domain.com",
        "Type": "L2TP-IPsec",
        "IPsec": {
          "AuthenticationType": "PSK",
          "IKEVersion": 1,
          "PSK": "my_psk",
          "Recommended": [
            "PSK"
          ]
        },
        "L2TP": {
          "Username": "my_username",
          "Password": "my_password",
          "Recommended": [
            "Password"
          ],
          "SaveCredentials": true
        }
      }
    }
  ],
  "Type": "UnencryptedConfiguration"
}