Sonic → Please help me configure modem to work with router

For the past three years, I've been using the Motorola modem Sonic.net supplied me, and it's worked just fine with my Linksys WRT54GS router. Now, the modem has died and I have replaced it with a Netgear DM111PSP modem, and suddenly the connection gets dropped pretty regularly.

I suspect the problem is related to the combination of configurations in my modem and router. With the old set up, when I looked at the status page in the Linksys, the IP address showed the external IP address supplied by Sonic.net. Now, it shows the LAN IP address of the Netgear modem. Am I correct that this is a problem? If so, could it be causing the intermittent connectivity problems?

I'm also noticing that both my router and modem are configured to act as the DHCP server. I'm guessing this is also a problem.

I'm at the end of my wits. Can someone please help?

Having both modem and router acting as DHCP server is not a problem in its own right; the LAN devices behind the router won't see the modem DHCP server. But, along with the modem assigned private IP address, it indicates that the modem is not acting as a bridge, which was probably the configuration of the Motorola.

As currently configured, if this is PPPoE ADSL, make sure that you don't have both devices trying to establish the PPPoE session; only one device should do that.

It would be better, if it is possible at all, to bridge the Netgear. I can't help you with the Netgear specific details because I don't have that device.