Ipsec_conf.vim is a project mainly written in Vim Script, it's free.
Syntax highlighting for FreeS/WAN ipsec.conf
This is a mirror of http://www.vim.org/scripts/script.php?script_id=312
Highlights keywords, IP addresses, numbers, and strings in FreeS/WAN's (http://www.freeswan.org/) ipsec.conf configuration file.
Somewhat validating: it flags unknown constructs as errors in red.