Cisco IPSec forgets password (Mavericks)
Per this question, it's not so much a problem with the OS as a problem with the configuration of the VPN on the server side.

One of the options your IT admins can do is force passwords to not be remembered for the VPN connection, and the OS X client will honor this setting. If you have the keychain open and are looking at the saved password when you connect, you can actually see the saved password disappear when you connect to the server.

I've searched for a way around this going so far as trying to applescript the login window, but they've blocked that avenue is well.