From ArchWiki

vpnc is a VPN client for Cisco hardware VPNs.


Install the vpnc package.


The vpnc configuration files are in /etc/vpnc. It contains a default.conf file that you can copy and modify for your setup.

Executing vpnc --long-help will provide the names and descriptions of the various configuration options. For instance, in that output you will see

 --gateway <ip/hostname>
     IP/name of your IPSec gateway
 conf-variable: IPSec gateway<ip/hostname>

which translates into a line like this in your configuration file:

IPSec gateway gateway.example.com


The vpnc package comes with a systemd unit vpnc@.service. If you want to use the configuration file /etc/vpnc/client.conf, you would start vpnc@client.


In case the vpnc client crashes with:

   May 15 09:11:38 ntrp-mimacom systemd-coredump[5858]: Process 5814 (vpnc) of user 0 dumped core.
                                                        Stack trace of thread 5814:
                                                        #0  0x00007f835cba3a10 raise (libc.so.6)
                                                        #1  0x00007f835cba513a abort (libc.so.6)
                                                        #2  0x00007f835cb9c607 __assert_fail_base (libc.so.6)
                                                        #3  0x00007f835cb9c6b2 __assert_fail (libc.so.6)
                                                        #4  0x000000000040e48c n/a (vpnc)
                                                        #5  0x0000000000412348 n/a (vpnc)
                                                        #6  0x0000000000404f72 n/a (vpnc)
                                                        #7  0x00007f835cb90511 __libc_start_main (libc.so.6)
                                                        #8  0x000000000040596a n/a (vpnc)

you will need to monkey patch the the software because an assertion is failing with the latest updates..

Download the sources from https://svn.unix-ag.uni-kl.de/vpnc/trunk/ and patch the file vpnc.c with the following:

   Index: vpnc.c
   --- vpnc.c      (revision 550)
   +++ vpnc.c      (working copy)
   @@ -1206,7 +1206,7 @@
           assert(a->af == isakmp_attr_16);
           assert(a->u.attr_16 == IKE_LIFE_TYPE_SECONDS || a->u.attr_16 == IKE_LIFE_TYPE_K);
           assert(a->next != NULL);
   -       assert(a->next->type == IKE_ATTRIB_LIFE_DURATION);
   +       /* assert(a->next->type == IKE_ATTRIB_LIFE_DURATION); */
           if (a->next->af == isakmp_attr_16)
                   value = a->next->u.attr_16;

Temporary workaround found here: https://bbs.archlinux.org/viewtopic.php?id=225556

Remember to change the PREFIX to /usr instead /usr/local so you overwrite the broken binary.