enchesss ->
I have an identical adsl connection like that the one you describe - a pppoa adsl modem modem running in bridge mode, with a SME 7.2 gateway behind that. I rceive the external ip dynamiccally from my isp and I run a periodically cronjob to keep a dyndns dns server updated. I also have the selintra iptelephony server installed on the SME 7.2 gateway, and I rally feel I got a lot out of a cheap solution and a cheap adsl line.
It's a bit time since I sat up the ADSL modem, that used to be a router, but that is now a bridge, but I will try to remember ..
I think I first devided the "project" into two parts: 1. The problems related to the SME gateway. 2. The problems related to the adsl router/bridge/modem.
I think I started with the adsl modem. First I just disconnected the SME server and connected a Windows workstation directely to the adsl modem to make the bridging working in such a way that it would deliver the external ip directly into the Windows workstation.
This apeared not to be to easy. After a lot of thesting I had to give up my forst adsl modem and buy myself another one. The second one I think is a Billion Bipac 5102s (An old modell just now.). Also in this case I had to do some mailing to the Billion factory to get a "special firmware" to make the proper bridge mode possible. After upgrading the firmware to the ADSL modem no 2 I was then able to receive the external ip to the Windows workstation.
At this point it was just to plug in the SME 7.2 gateway and a switch over, and everything was just working fine.
I think that the task of making a adsl ppoa modem to work properly in bridge mode has little to do with the SME box itself, but it has a lot to do with the type and brand of the adsl modem. If I should do it again I would use the trick to make it work from a Windows workstation first, before I would try to connect in the SME 7.2 gateway.
Of cource one should be avare of that the Windows workstation will be exposed for a major treat when it is connected directly to the net, for the mentioned testing reasons. Firewalls etc has to be applied as required.
It took a few workhours to make it all working, but it works really good when it first work. (The main reason for doing this for me was to have the Asterisk iptelephony server connected directly to the net via the external ip, without the need of paying extra for such a service.)
I think I worked 2 monts or something on this "bridge mode problem", but none of these problem apeared to be related to the SME gateway. It was all related to the brand, model, firmwarestatus and configuration of the adsl modem.