OK, I think I am in the ‘last chance saloon’ for Zs on this now:
From what I have read, my ETH00 WAN interface does not need a fixed IP address assigned if it is bound to PPPoe and my ISP provides a Dynamic IP.
I reconfigure the PPPoe interface with my DSL username, Password then reboot/refresh Zs.
After about 30 seconds I get a PPPoe connection with inet and p-t-p addresses given. I ping an external web URL from the ETH01 LAN side and get a good result.
Then I reboot Zs (simulated mains fail!) with the DSL modem still connected and get PPPoe connected, but cannot ping the same URL. (no web browsing).
Then I hit PPPoe Configure/Save/refresh. The inet and P-T-P addresses change and I can now ping the URL.
So please help! Why does my PPPoe to ETH00 WAN binding appear to be lost and not automatically refreshing after a Zs reboot?