Hey guys,
I have the 3800 with backfire 10.03.1 on it.I want to connect my Thomson modem with the 3800 router and have Internet access.
I have connected via ethernet the thomson with the 3800(in its WAN port) and via ethernet the 3800 with the PC.

The Thomson is configured to its default values.It is configured in PPPoE and the Dynamic DNS is disabled.
It has a primary and a secondary DNS active.

The 3800 is also currently configured in its default values,with which I have no Internet access.
WAN's protocol is DHCP client.The interface enabled is eth1(wan).
LAN's protocol is Static IP with the default value 192.168.1.1 and the default netmask.The DHCP sever is enabled starting from 100 and ending to 150.The bridge interfaces option is also enabled for the VLAN and the two wireless interfaces.

Also one more thing.When I connect the 3800 with its original firmware I have Internet access.Howver before that i get the message : to avoid conflict with your ISP the router's IP is set to 10.0.0.1
I tried this with backfire on, but it resulted into losing communication with the router.

As I said I am still an amateur, so any help will be greatly appreciated.
Thanks.

Which ip does your Thomson have?

Default gateway is 192.168.1.254
DHCP range of Thomson spreads from 64 to 253
At the moment I am connected only to the thomson router.
3800 is out of the way till I figure a way to configure it.

(Last edited by dimigiotas on 3 Nov 2012, 22:20)

Can you configure the Thomson TG585 in bridge mode?

If yes, you can use PPPoE on the NETGEAR WNDR3800.

Yes Thomson can be configured in bridge mode.
Do I need to modify the connection between the routers after I set it to bridge?

Once you configured the Thomson TG585 in bridged mode you can configure PPPoE on the WNDR3800's WAN interface.

(Last edited by written_direcon on 3 Nov 2012, 22:56)

Ok.I will get back to you on that.
Thanks.

*EDIT
Out of pure curiosity;Is this the only way to make this setup work,or are there alternatives?

(Last edited by dimigiotas on 3 Nov 2012, 22:58)

If you change the IP of Thomson to something like 192.168.0.1, different from OpenWrt Router you must be good.

If you have PPPOE connection Bridging your Thomson is a good solution so it will be OpenWrt connecting the internet.

Well I didn't have to bridge the Thomson after all.
I changed the LAN port settings of the 3800 (IP,Default Gateway,DNS),in order to avoid IP collision
and it worked perfectly.
Anyway,thank you both for your time and eagerness.Much appreciated.

Then you have a double NAT situation. This is not so good!

What do you mean?Where can this cause problems?
I have no connection problems so far.