I have successfully set up L2TP/IPsec servers on my ER707-M2 gateways.  I am using these VPNs for remote access to branch office sites if our IT team needs to access things on the local network (typically printer web interfaces).

I am using the Windows native L2TP/IPsec VPN client.  It works great - EXCEPT if I try to make the connection from a client connected behind one of the ER707-M2 gateways. So the VPN connections work great when working from home, but not from work!

I suspect that the gateways are not doing NAT properly for L2TP clients (e.g. L2TP passthrough), but it could easily be something else.

Has anyone else faced this?