I'm trying to setup a new Vigor 2930 with two DSL connections with a bonded IPSec VPN connection to a central office with a Cisco ASA 5520 box.

I can bring individual VPN tunnels up and use them successfully, but when I trunk them on the 2930, they stay up, but traffic just disappears. I suspect it's something to do with the routing on the ASA - it won't know which VPN tunnel to send the traffic over, as they both go to the same remote network. At least, that's my newbie interpretation of what's going on.

Is this possible, or do I need a 2930 at both ends of the trunk?

What does the cisco asa say when you look at the negotiation logs for each tunnel? Are you using static or dynamic crypto maps on the asa? (Ie using a static IP or dynamic one on the draytek side )

I've never tried doing bonded interfaces over vpn, are you sure the cisco will suport this behaviour?