Call me slow, but I found that XDA thread very hard to follow.
Since I managed to get Cisco VPN going on my Incredible, I thought I'd try to lay out what I did in case it helps other slow people.
Now let's get down to it.
First, I didn't deal with installing any special tun.ko as described in XDA. I found that all of the KinxKernels located here have it pre-installed:
KiNgxKernel - The Incredible List
So I installed a kinxkernel. I am also running Skyraider ROM, but I don't think it matters as long as you have a kernel (such as Kinxkernel) that has tun.ko.
Next install VPN Connections from the market. Note I could never get the "VPN Connections" GUI to work correctly, and it seems that many people have this problem. So I got it going with scripts instead. To use these, you will need a terminal emulator such as "Better Terminal Emulator." Download that from the market.
Now you need to create a file called vpn.conf in the /sdcard root directory. (I just created the file on my PC, connected the SD card, and stored it there.) The file should look like this (fill in your own info for gateway, group name, etc.):
IPSec gateway <gateway>
IPSec ID <group name>
IPSec secret <shared secret>
Xauth username <user name>
UDP Encapsulate
Then create a script called "go" in the /sdcard root directory. It should look like this:
/data/data/org.codeandroid.vpnc_frontend/files/vpnc /sdcard/vpn.conf --script /data/data/org.codeandroid.vpnc_frontend/files/vpnc-script --pid-file /sdcard/vpnc
Now go into your terminal program and type the following:
su
mkdir /dev/net
ln -s /dev/tun /dev/net/tun
All the stuff up until now is "one time only" as you get everything set up. The following must be done each time you want to start the VPN
First, to get tun.ko going, start up your terminal emulator program and execute the following commands. (NOTE: From what I gather, tun.ko can be installed in different locations depending on kernel. This specifies the correct location for kingxkernel):
su
insmod /system/lib/modules/tun.ko
To verify tun.ko is working, you can then run:
lsmod
It should say something similar to "tun 10734 0 - Live 0xbf000000"
Then type the following to start the VPN:
sh /sdcard/go
You will then be prompted for a password. Enter that, and your VPN should be up and running.
While I figured out these steps from numerous different sources, particular credit goes to pvlagsma on XDA...who provided a lot of this info. Hope it helps some lost soul!