Nathaniel Jacobsen's blog

VPN on x86_64 Linux

So, I recently got an Athlon 64 box and put pure 64-bit Gentoo on it, but then I couldn't get CiscoVPN to connect. Apparently, there's an open source solution that works for the Cisco 3000 VPN boxes, and it's called VPNC. Look at the whole entry for setup instructions.

It's really easy to setup, just download it, make && sudo make install, and setup up your conf file like so (I'm not going to publish the specifics, just the required entries. If you're associated with Case, you can get the information needed to connect from the casevpn.pcf file):
/etc/vpnc.conf:

IPSec gateway *****.case.edu
IPSec ID ****
IPSec secret *****
Xauth username nxj18
Xauth password *****

Where the gateway is the server you connect to, the ID is in the pcf file, the secret is the group password (you can get that from a network admin if you ask nicely, or you can hack the casevpn file and decrypt it yourself), and your password is your Case network password.

Next, make sure you have the tun module compiled and load it before you run the vpn. It's CONFIG_TUN, and I have it set as a module:

/usr/src/linux/.config:
CONFIG_TUN=m

Finally, you can manually start the VPN client as follows:

$ sudo modprobe tun
$ sudo vpnc-connect

and similary disconnect:

$ sudo vpnc-disconnect
$ sudo rmmod tun

Or use this handy init script (for gentoo):

#!/sbin/runscript

depend() {
need net
}

start() {
ebegin "Attempting to load IP tunnelling"
/sbin/modprobe tun &>/dev/null
eend $? "An error occurred while attempting to load tunnelling"

ebegin "Instantiating VPN client..."
vpnc-connect &>/dev/null
eend $? "An error occurred while attempting to start VPN."
}

stop() {
ebegin "Disconnecting VPN client"
vpnc-disconnect &>/dev/null
eend $? "An error occurred while attempting to disconnect"

ebegin "Unloading module tun"
/sbin/rmmod tun &>/dev/null
eend $? "An error occurred while unloading module tun"
}

That's it, it's a piece of cake.