I'm using a RUT240 to configure an IPsec/L2TP VPN connection, and it didn't work.
I figured out that the problem was the missing of "leftprotoport=17/1701" and "rightprotoport=17/1701" parameters in strongswan ipsec configuration file (/etc/ipsec.conf). In your router, this file is generated automatically from some kind of configuration script and it's a syslink to /tmp/ipsec/ipsec.conf file.
I need to do that in permanent way (reboot persistent), better from the web configuration page. I saw that there is a "custom options" in IPsec conf page, but any string i write in this field nothing goes in /etc/ipsec.conf.