We've got a new Vigor 2850, an ADSL link a (ISP A/29, currently on a different ADSL modem/router), and a new VDSL link b (ISP B/29).

Currently, using a separate Linux-based firewall, we NAT (and filter) some incoming traffic to some A/29 addresses onto specific servers and services.
and our outgoing traffic from internal LANs is NATted onto ISP A/29 as well.

We'd like to use our new VDSL link b, send a bit of traffic out of the ADSL link a (optional - a nice to have, maybe we'll end up using load balancing policies and just send our VOIP traffic, plus there for the failover), maintain incoming access to those A/29 addresses over link a (until/if we migrate our external users), and introduce some incoming access to B/29 addresses over link b?

It's a bit unclear from the manual as to how two IP subnets, one from each WAN link, interact with the load-balancing - obviously the Vigor is going to have to NAT something if it comes from address space A but wants to 'balance it' down link b, and it must maintain incoming sessions over link a.

I've found other posts in this forum about configuring multiple WANs (e.g. http://www.forum.draytek.co.uk/viewtopic.php?f=2&t=17190&p=72047), and I've also read posts explaining how to configure a single IP routed subnet (e.g. http://www.forum.draytek.co.uk/viewtopic.php?f=2&t=18131)

I can see that we're probably going to have to have A/29 and B/29 subnets on different ethernet ports of the Vigor - ideally we'd just send them out on the same physical LAN port, and handle them on our firewall as we do today, but if we have to add an extra NIC or a switch in there then so be it.

But how the IP subnets are best configured to interact with the load balancing is not yet clear to us. (If necessary we're not averse to NATting the outgoing traffic onto a third, private IP subnet range, if that helps.)

Has anyone got something similar up and running, and have any advice for us?