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I'm helping my dad move to Earthlink DSL from dialup. As part of his package they sent a DSL modem (Zylink, or some brand like that) and I'm supplying a D-Link wireless router to act as the PC/modem go-between and to serve as a firewall. I used this same router at home before upgrading to a newer D-Link.

Problem: I cannot get the D-Link to speak with the DSL modem. Their respective IP addresses are 192.168.0.1 (D-Link) and 192.168.1.1 (DSL modem) but they won't communicate if I put an ethernet cable between them. The D-Link offers a feature to ping IP addresses you enter but when I enter the modem's address the D-Link says it can't ping it.

I've reset the D-Link to factory default settings but even so, I can't ping the DSL modem. I don't believe I have any firewall rules established that would prevent this--I've looked closely and compared with my current D-Link settings at home.

I can connect my dad's PC directly to the DSL modem, using the same ethernet cable the DSL modem and D-Link speak with, and he can surf the internet if we do this. (He can also ping the modem.) So all signals indicate a working line and DSL modem. Obviously however I'd like to get the D-Link between the PC and modem, for protection.

Dad's connection to Earthlink will be via dynamic PPPoE and I have his username and password ready to go. But if the D-Link can't reach the DSL modem that's a bit of a moot point.

Do you have any ideas what's preventing the modem and router from communicating? Thanks for any and all suggestions.

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3 Answers 3

up vote 5 down vote accepted

This is probably down to your subnet being /24 or 255.255.255.0, basically this means that 192.168.0.1 and 192.168.1.1 are effectively on two separate networks.

When you use two devices (especially consumer gear) it can cause a lot of trouble. From what I have gathered, the ISP supplied modem is actually a router as it provides a private IP address and does not simply act as a modem.

I would check to see if you can disable NAT and/or change the mode so it acts as a real modem and not a router as right now - this way, your D-Link will simply see an external IP and do all the router functions.

If it is not capable of going in to a simple modem mode, you will have to look at bridging or similar.

Lastly, if you really want to have two devices, you can just change the subnet to 255.255.0.0 or change the ip of one of the devices to be on the same network, however, again, when you have things such as double NAT, it can lead to a lot of trouble.

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+1 subnet is the first thing that came to mind, although I was on a handheld device and typing would have taken a while :) –  John T Jan 24 '10 at 7:30

. Their respective IP addresses are 192.168.0.1 (D-Link) and 192.168.1.1 (DSL modem) but they won't communicate if I put an ethernet cable between them.

Are they on the same subnet?

From the sounds of it, you need to put the modem into bridging mode and then have the router initiate the internet connection.

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+1 same reason as my other comment –  John T Jan 24 '10 at 7:31

192.168.0.1 is the local IP address of the modem

192.168.1.1 is the local IP address of the router (which is irrelevant for the modem).

make sure the modem is connected to the WAN port of the router and not to any of the 4 (?) LAN ports.

you may have to change the router WAN IP accordingly (e.g. to 192.168.0.2 with 192.168.0.1 as gateway, or assigned by DHCP). you should be able to configure the router manually, or use the setup wizard provided by D-Link. if you don't have the CD, i'm sure you can download the program from D-Links support website.

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