Description of problem:
VPN-Connection to FritzBox not possible

Version-Release number of selected component (if applicable):
vpnc-0.5.3-22.svn457.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
1. Use NetworkManager-vpnc-plugin to setup VPN-Tunnel to FritzBox
2. Kick off graphical start of VPN-Connection
3.

Actual results:
VPN Connection to FritzBox not possible (logs below)

Expected results:
Proper VPN Connection established

Additional info:

Similar behaviour expected when used without graphical interface but didn't try myself.

According to comments I've read SVN469 should be sufficient to work.
Positively tested with SVN550 myself.

Logs from SVN457 from EPEL7:

Sep 18 18:01:35 kwenning.muc.csb NetworkManager[1368]: <info>  [1505750495.7792] audit: op="connection-activate" uuid="1543828c-4947-4381-8b17-7d6911b6e1ec" name="wekac-vpnc" pid=4708 uid=27270 result="success"
Sep 18 18:01:35 kwenning.muc.csb NetworkManager[1368]: <info>  [1505750495.7845] vpn-connection[0x562a2f8ac4e0,1543828c-4947-4381-8b17-7d6911b6e1ec,"wekac-vpnc",0]: Started the VPN service, PID 8274
Sep 18 18:01:35 kwenning.muc.csb NetworkManager[1368]: <info>  [1505750495.8050] vpn-connection[0x562a2f8ac4e0,1543828c-4947-4381-8b17-7d6911b6e1ec,"wekac-vpnc",0]: Saw the service appear; activating connection
Sep 18 18:01:35 kwenning.muc.csb NetworkManager[1368]: <info>  [1505750495.9188] keyfile: update /etc/NetworkManager/system-connections/wekac-vpnc (1543828c-4947-4381-8b17-7d6911b6e1ec,"wekac-vpnc")
Sep 18 18:01:39 kwenning.muc.csb NetworkManager[1368]: <info>  [1505750499.4131] keyfile: update /etc/NetworkManager/system-connections/wekac-vpnc (1543828c-4947-4381-8b17-7d6911b6e1ec,"wekac-vpnc")
Sep 18 18:01:39 kwenning.muc.csb NetworkManager[1368]: <info>  [1505750499.4141] keyfile: update /etc/NetworkManager/system-connections/wekac-vpnc (1543828c-4947-4381-8b17-7d6911b6e1ec,"wekac-vpnc") after persisting connection
Sep 18 18:01:39 kwenning.muc.csb NetworkManager[1368]: <info>  [1505750499.4234] vpn-connection[0x562a2f8ac4e0,1543828c-4947-4381-8b17-7d6911b6e1ec,"wekac-vpnc",0]: VPN connection: (ConnectInteractive) reply received
Sep 18 18:01:39 kwenning.muc.csb NetworkManager[1368]: <info>  [1505750499.4324] vpn-connection[0x562a2f8ac4e0,1543828c-4947-4381-8b17-7d6911b6e1ec,"wekac-vpnc",0]: VPN plugin: state changed: starting (3)
Sep 18 18:01:39 kwenning.muc.csb NetworkManager[1368]: <info>  [1505750499.4767] manager: (tun0): new Tun device (/org/freedesktop/NetworkManager/Devices/19)
Sep 18 18:01:39 kwenning.muc.csb NetworkManager[1368]: /usr/sbin/vpnc: response was invalid [2]:  (ISAKMP_N_INVALID_PAYLOAD_TYPE)(1)
Sep 18 18:01:39 kwenning.muc.csb NetworkManager[1368]: <warn>  [1505750499.7410] vpn-connection[0x562a2f8ac4e0,1543828c-4947-4381-8b17-7d6911b6e1ec,"wekac-vpnc",0]: VPN plugin: failed: connect-failed (1)
Sep 18 18:01:39 kwenning.muc.csb NetworkManager[1368]: <warn>  [1505750499.7411] vpn-connection[0x562a2f8ac4e0,1543828c-4947-4381-8b17-7d6911b6e1ec,"wekac-vpnc",0]: VPN plugin: failed: connect-failed (1)
Sep 18 18:01:39 kwenning.muc.csb NetworkManager[1368]: <info>  [1505750499.7411] vpn-connection[0x562a2f8ac4e0,1543828c-4947-4381-8b17-7d6911b6e1ec,"wekac-vpnc",0]: VPN plugin: state changed: stopping (5)
Sep 18 18:01:39 kwenning.muc.csb NetworkManager[1368]: <info>  [1505750499.7412] vpn-connection[0x562a2f8ac4e0,1543828c-4947-4381-8b17-7d6911b6e1ec,"wekac-vpnc",0]: VPN plugin: state changed: stopped (6)
Sep 18 18:01:39 kwenning.muc.csb NetworkManager[1368]: <info>  [1505750499.7439] vpn-connection[0x562a2f8ac4e0,1543828c-4947-4381-8b17-7d6911b6e1ec,"wekac-vpnc",0]: VPN service disappeared