chromeos/test/data/network/valid_l2tpipsec.onc

{ "GUID": "guid",
  "Type": "VPN",
  "Name": "MyL2TPVPN",
  "VPN": {
    "Type": "L2TP-IPsec",
    "Host": "some.host.org",
    "IPsec": {
      "AuthenticationType": "PSK",
      "IKEVersion": 1,
      "PSK": "some_preshared_key",
      "SaveCredentials": true
    },
    "L2TP": {
      "Username": "some username",
      "Password": "some password"
    }
  }
}