Hello.
I have an ISA Server 2006 at main office and a DFL-210 at Branch office.
I need to connect branch office to main office by site-to-site sheme.
But i have one small nuance: at branch office i cant get public IP address.
So i cant use IPSEC tunneling mode.
But i cant find any solution or step-by-step instruction or how-to use L2TP over IPSEC CLIENT in DFL-210.
What I've already done:created site-to-site network on ISA,
on DFL-210 created IPSEC in transport mode


 and L2TP client

tic "Automatically add a route for this interface using the given remote network." 
and   "Add route for remote network"
SA successfully established but only when i ping from DFL-210 to udp port 1701 of ISA, 
L2TP client stay in state 
Type :   Single client tunnel
Sessions :   1
Tunnel status :   Connecting
Session status :   Establishing
And in ISA Monitoring - there is no connecting to port 1701 (except udp ping).
I need help because i dont know where to look now...
And sorry for my bad english.