In my previous post, I described how to set up an IPSec/L2TP server which OS X can connect to out of the box. It seems like IPSec/L2TP has become a popular choice of VPN, given its native support in Windows 7, OS X, iOS and Android. So you think it'd be easy to get Linux connected too, yes? Apparently not. There's a package called l2tp-ipsec-vpn which is supposed to make life easy, but unfortunately it requires Openswan which again requires kernel patches, which I loathe (despite once upon a time patching my kernel several times a day).
All this drove me to write a quick script to connect to an IPSec/L2TP-based VPN using the in-kernel IPSec implementation. The result is here for those who might also find it useful:
Using it is trivial, assuming all goes to plan. And when you need to debug, it prints all the debugging information you might need right to your console. How useful is that?