i am trying to setup a lan to lan tunnel between a draytek 2820 and a juniper SSG520.

the tunnel initiates ok (phase 1 and 2 ok) but no traffic passes between either side.

the juniper side of tunnel is NAT'd but the draytek is not.

DrayTek syslog has a message:-
NAT-Traversal: Using draft-ietf-ipsec-nat-t-ike-02/03, no NAT detected.

Can anybody help with this?
Draytek is running firmware: 3.3.4_232201

Regards,
Chris.