Got a little complicated whilst writing this - 1 refers to your modem, 2 refers to your wireless router.
This is one thing I hate doing as it can change based on device manufacturer and features. Personally, if you can upgrade 1 and 2 and just have one device, you will be better off.
For a start, if your 2 actually supports this e.g. has an Ethernet WAN port instead of a smaller telephone line adapter, you may not even have to disable DHCP anywhere - simply make sure the 1 works (connect it up to one pc) and if it does, plug it in to to the 2, and then it should "just work" - if it doesn't, your 1 is more likely to be an actual router (just with one port).
so, if 1 is actually a router instead of a modem, I would recommend that you see if you can change the mode of 2 and basically disable all routing and change it to an access point
, this will then do all the DHCP and everything else at 1 whilst just providing an access point to wired and wireless devices - by far the best way. (After changing this, you may have to first manually set the ip of 2, this will mean that all devices are pingable and accessible on your network and the easiest to manage.
Is the ADSL device a modem or a router? Your question text and the title seem to conflict. – squircle – 2010-03-04T21:24:02.737
In addition to what the purple pixel said above, name the model of the "model" (which I'm guessing could be "modem"/router) – Rook – 2010-03-04T21:31:13.160
Yes, thanks for pointing the error. Now fixed. – Eduardo Molteni – 2010-03-04T21:49:33.847
I'm trying to avoid bringing specifics models of routers to learn about the process, but I guess it is different in every case. Weird – Eduardo Molteni – 2010-03-04T21:51:04.030
Actuaally, it's rather similar in most cases. But while learning, it is better to view one specific example (model), than to go "the general route". – Rook – 2010-03-04T22:32:23.043
http://superuser.com/questions/104043/extend-network-by-connecting-a-wireless-router-to-a-wired-router/104056#104056 possible dupe BTW. The answer/answer is identical – Journeyman Geek – 2010-03-04T23:51:55.833