How to connect a cable modem to the DI-LB604


Recently my old cable modem stopped connecting to the internet. The modem lasted about 8 years so I am sad to see it go. I called my cable company and they sent a technician to my home to check out my internet trouble. The technician said my signal strength was fine. He went out to his truck and brought back a new, rental modem and connected it to my cable. His modem worked and connected to the internet. So, we concluded that my old modem must have died.

I had this new cable modem connected to my DI-LB604 D-Link router for several days with no problems. I didn't have to make any adjustments to the router to get the router to acknowledge the new modem. It just worked. But then, a few days ago, it stopped working. The dual-WAN router sees my DSL modem, but it does not see the cable modem. What happened?

The cable modem is a Motorola SB5101

The router shows an active LED for the DSL router on WAN 2, but the cable connection on WAN 1 is dead... the LED's for WAN 1 are off.

So, how am I going to fix this? How can I get the router to see that WAN 1 is connected to my cable modem? Here was my solution...

Enable both WAN connections

I guess if WAN 2 is set as a backup, then when WAN 1 comes online, the router disconnects from the "backup" WAN 2. That makes sense.


If you want your router to actively use both WAN 1 and WAN 2, then make sure you enable them... don't make either of them a "backup".

But, why was the router working fine with two internet connections for several days and then suddenly stopped working? I didn't make any change to the router settings to cause it to go offline originally. It's possible the router got rebooted during a power failure, but I don't know for sure. My guess is that it has to do with getting a new cable modem several days before the router failure. Maybe putting a new cable modem into the router requires a MAC Address change. If the router did get rebooted, then maybe the router realized that the cable modem changed and it didn't like using the same MAC Address for the new modem.

It's strange, but the MAC Address on the bottom of the modem does not match the value I entered into the router settings. When I tried to use the MAC Address on the sticker on the bottom of the modem, the router didn't like that, either. If changing one of the modems, it may be necessary to change the MAC Address to a new value, one that is similar to the router's MAC address, with just the last digit being different.

The router is using both of the internet connections, both DSL and cable. The router has been running well for several months with these settings.


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