I tried and failed. I found a thread on another well known broadband message board on how to do it but got stuck.

Firstly I changed the 612's IP to 192.168.2.1 as my DD-WRT router is 1.1

Changed the HG612 to PPPOE_Bridged and removed the LAN port requirement from LAN1.

I then tried to add a static route in DD-WRT and that's where it went all wrong. I lost PPPOE completely somehow.

Did you mean 2.1? 2.1 and 1.1 would be in different subnets normally.

Yeah the guide I read said to stick the HG612 in it's own subnet and then setup a static route on the router.

You don't need a static route as all routes are on the router anyway and it doesn't need to know of a route on another router. However each router is different and DD-WRT seems to require some iptables mangling according to this wiki.

I also found that DHCP doesn't work with the HG612 properly, and you need to set up a static IP to the interface.

I'm confused now.

So I don't need to put the HG612 in it's own subnet?

I didn't when I was monitoring mine.

In normal use the HG612 does not have any user visible IP addresses. It's as transparent PPPoA to PPPoE modem.

When using the second ethernet port on the HG612 for monitoring I simply gave it an unused IP address on my LAN and connected it to my LAN. No need for routing or anything else.

I know that bit, I want to access the stats through the LAN1 cable. Not run a second cable from LAN2.

It's best to have the HG612 on a separate network from the internal network as the router will otherwise get very confused routing-wise ie

HG612------<LAN1>--------Router-------<LAN2>------internal devices

Here I've got the HG612 as static 192.168.1.1, the WAN interface on the router as 192.168.1.3

The router's LAN interface is set up as 192.168.100.1, and DHCP serves addresses to the 192.168.100.0/24 range.

Like you I've got the HG612 and the router some distance apart - in my case through Powerline adaptors.

If you need more info on how I've got the HG612 setup shout and I'll forward some screenshots.

This is how I did it:

https://support.aa.net.uk/Router_-_EchoLife_HG612