Hello David, please read below for my answers.
YOU Wrote:
To make the system work where the remote users access the Internet via their own DSL link, and other domain traffic to the leased line between the two locations, use need a switch at each location. Your switch must route internal traffic to the switch at the other end of the leased line and send Internet traffic to the local DSL modem.
My answer: We don't have a dedicated switch to distribute and balance traffic to either Cisco router or ADSL router. We take advantage of the "Static Route" function on the ADSL router. The traffic is all directed to the ADSL router first, and in turn directed to the Cisco router if the destination IP falls into any of our internal subnets.
You wrote:
As a fall back, the remote switch should be set to route the Internet traffic to the Domain side if the remote DSL is not available, and the domain switch can do the same the other way if the domain Internet access goes down.
My answer: Similar to what you said, the bi-directional routings are configured on the ADSL routers residing at both sites.
You wrote:
To see the domain, the DNS in the remote area needs to point to the Domain DNS server only, and the Domain DNS needs to point to itself and then to the Internet DNS to resolve the traffic for both locations. That way users at the remote location will resolve other Domain assets, etc.
My answer: it's the thing I wanna put under control. I haven't messured (no idea how as well

) the amout of traffic for the remote DNS lookup, but I assume it won't be alot as long as the surfing part doesn't go back and forth along our E10 pipes.
You wrote:
DRAW OUT A DIAGRAM and label all the IP interfaces, and it should become clearer. If I understand your description correctly, you have a network at each location that has a dsl modem connected to the LAN at that location, and you have a leased link between the two sites (which has a switched router on each end???) which connects both the LANS together.
My answer: Sorry I don't know how to draw a diagram for you guys. But you are right to understand our network layout, and our LANs are connected via Cisco routers (2600 series).
You wrote:
The big question missing here is WHERE ARE YOUR FIREWALLS??? You need one between the Internet and the LAN in both locations, but nothing has been mentioned here. Is you firewall part of the switch, or a box by itself (Please dont say "What firewall"....)?
My answer: I shouldn't call our firewall as ADSL router from the every beginning. My appology for the confusion! If I don't enable intrusion detect/service filters/etc., it will function like a regular ADSL router. Anyway, the firewall (ADSL router) is in front of all the internal resources. Each branch has one such firewall.