Sorry for the very long question but in this case lots of details are necessary.
Problem: My crappy Thomson TG585v7 DSL modem/wifi/LAN router reboots many times daily. I think it's because the custom ISP firmware can't handle the traffic on my home network (LAN: 1 media center pc; wifi: 1 netbook, 1 desktop, 3 wifi music players, 2 smartphones).
The firmware is locked by the ISP so cannot modify or upgrade it. Instead, I want to connect a Linksys WRT54G v7.1 wifi/LAN router to the modem. The plan is to have the "stupid" modem only talk to the more competent WRT54G which will handle all the actual network stuff. I hope that the modem will cope with just one client and the Internet traffic.
Both the modem and the WRT54G can do DHCP, so I think that one of them must be disabled.
The modem is hardwired to 10.0.0.138 (on 255.255.255.0) and the WRT54G uses 192.168.1.1 by default but can be freely changed. Is it correct to disable DHCP on the WRT54G so that only the modem provides this service?
1) I guess I must change the WRT54G to e.g. 10.0.0.139 in order to bring it onto the same network, right?
I tried that, and promptly lost connection to it. Only a hard reset brought it back, but with factory defaults.
I can configure a WLAN on either the modem or the router (let's not discuss having a public WLAN on the modem, and a private WLAN on the router). I want to disable the modem's WLAN so that only the WRT54G connects to it. I tried that, but then I couldn't reach the modem (through the WRT54G) anymore.
2) How do I set up the WRT54G to provide access the modem, and to provide Internet access?
I've tried to set up a LAN&WLAN on the WRT54G and that worked fine, but without Internet access.
3) How do I set up the WRT54G to route Internet traffic to the modem?
The final touch would be
4) How to have the WRT54G provide DHCP instead of the modem?
But since the modem's IP is hardwired, I don't know how that could work. I tried using DHCP on only the WRT54G but then wasn't able to reach any network devices.
The third question is the most problematic of them all, to me, and is where I need help most badly. If I get the above 3 questions sorted out but fail on the fourth, it is still a victory.
As a final note, it would be interesting to put a custom firmware (like Tomato) on the WRT54G, but I'll be happy if I get the network up and running without any hacking.
Best Answer
It sounds like what you want to do is put the modem into transparent bridging mode, which would cause it to just act like a modem and not have any other configuration. Just by googling I found some instructions on a forum for your model of modem, though I haven't tried it myself since I don't have one. I can describe to you the general process that you need to follow, since that's how I have my modem and router set up.
When a modem is in transparent bridging mode, you enter the ISP PPPoE information on the router, and it connects directly and transparently through the modem. The modem doesn't get an IP address at all and the external IP of the router is your internet IP.
You would need to know your PPPoE DSL login information. It may be available in the modem's web interface, or you may need to call your ISP to get it. Once the modem is put into transparent bridging mode, you will want to configure the router with that information. The modem will no longer do DHCP, have a local IP, or anything of the sort - it will essentially be gone as far as your network is concerned, and your router will be the extent of your LAN. Make sure that the modem is attached to the router via the WAN port when you do this, not one of the LAN ports, otherwise it won't work.
Good luck, hopefully that helps you out. Make sure that you have access to a different internet connection somehow in case you make any mistakes so that you can come back to get help.