I am currently testing an RB411U as a home router. I have bridged ether1 and wlan1 for the home network. Ether1 is plugged into an 8-port D-Link gigabit switch. I have a Huawei E1820 HSPA+ USB modem on usb1 and an iBurst UTD (PPPoE) also plugged into the switch.

I was able to configure the ppp interface easily using the web interface, but I struggled to do the same for the pppoe interface.
Eventually I found using Winbox that the pppoe interface needs to be created on bridge not on ether1, but the web interface shows ether1 as the only available interface for the PPPoE Client.

so, the problem is: you cannot select a bridge as interface via Web, and you can do it with WinBox? did you use Webfig or Webbox?

so, the problem is: you cannot select a bridge as interface via Web, and you can do it with WinBox?

That is correct.

did you use Webfig or Webbox?

This was with Webbox.

Webfig allows me to enter anything I like in the 'Interfaces' field of the PPPoE Client, but the changes do not seem to be applied.
Feedback from support is that Webfig is still under heavy development.

in rc4 you should be able to do that in webfig. At least i am on testing version, so, do not be so grim.

Another problem that I was experiencing with 5.0RC3 was when using the PPPoE connection for internet instead of PPP, the PPPoE connection would drop and reconnect every time a wireless client connected or disconnected. This did not happen when I was using the PPP connection.

I missed 5.0RC4, but when 5.0RC5 was released I upgraded and the problem was resolved. Wireless clients could come and go and the internet connection would stay up regardless of whether it was PPPoE or PPP.

The other night I used Webbox to uncheck the 'Protect LAN' firewall option as I wanted to allow UPnP and suddenly the behaviour of the PPPoE connection dropping and reconnecting every time a wireless client connected or disconnected reappeared.

I see ROS 5.0RC6 has just been released. I suspect that upgrading might fix my problem.

Is there any way to dump my complete configuration in text format so that I can compare the configurations before and after the upgrade (and in future in case I break it in Webbox again)?

Of course.
http://wiki.mikrotik.com/wiki/Manual:Co ... figuration

Of course.
http://wiki.mikrotik.com/wiki/Manual:Co ... figuration

Thanks!

Unfortunately upgrading to 5.0RC6 didn't resolve the problem as I hoped.

I even tried downgrading to 5.0RC3, restoring a backup, then upgrading to 5.0RC5 but still I have the problem that every time a wireless client connects or disconnects the pppoe connection on the bridge interface drops and reconnects.
Now I'm not even sure that 5.0RC5 even fixed the problem.

Update: I have now also tried "downgrading" to 4.16 and the problem persists. This must be a problem with my configuration not with the 5.0 betas.

The problem of the PPPoE connection on the bridge interface dropping when wireless clients connect and disconnect turned out to be caused by the bridge MAC address changing. The solution was to set admin-mac to ether1's mac address and auto-mac=no for the bridge interface, similar to this thread:
http://forum.mikrotik.com/viewtopic.php?f=2&t=40518

Thanks to Sergejs of MikroTik support for this!