problems between cable modem and router
 

I have a wireless router (D-Link DI-524) and a cable modem (Motorola SURFboard 3100) which I cannot get to talk to each other. The modem works beautifully when connected to the computer via my Ethernet device (as it is right now), and the wireless router is also performing as expected on its own. When I try to connect the two, it appears that they don't want to communicate.

When I turn on the router, it appears to be exchanging some sort of data with the modem (flashing WAN light) for a few seconds, and then the light abruptly goes dead and stays that way. From the HTML configuration interface for the router, it looks like it can't find a DHCP server on the WAN connection.

The configuration page on the modem reports that everything is okay. It lists my Ethernet device's MAC ID as a known address, but nothing else. It reports that the onboard DHCP server is enabled.

All IP addresses are dynamic; the modem gets one from my ISP, the router is *supposed* to get one from the modem, and computers on the network get theirs from the router.

The most common answer I've seen to this sort of problem is that the modem has become somewhat fixated on the Ethernet device's MAC ID and needs some time to learn that of the router. I've tried all the sane permutations of the solutions I've found and given it plenty of time, but so far nothing seems to help. It sure looks like it's that sort of problem, though.

Is there anything else that might make this work, or am I just missing something obvious?

Re: problems between cable modem and router
 

Have you tried powering off the modem for at least 30 seconds? The steps that I would take, are to power off the modem and router for thirty seconds. Power up the modem. Give it 45 seconds or so to warm up. After that, plug in the router to the modem. Try that, and see how it goes. I have seen problems reconnecting cable modems to devices while powered on. Not all modems, nor all devices, but sometimes.

Re: problems between cable modem and router
 

A simple reset of your modem should work here.

Unplug your cable modem. Ensure the ethernet cable from the modem is plugged into your router. Ensure your router is turned on. Plug your modem back in. You've now reset your modem and it has detected a new MAC address (your routers' MAC address). That should fix it. If not, your ISP may have MAC address assignments at the DHCP level. If so, read on.

Call your ISP and ask if they assign IP addys according to MAC address of your NIC card (might be the case with static IP). If so, you'll be set if you tell them you have a router that you bought that you want to install..they should step you through setting it up.

TKS

Re: problems between cable modem and router
 

doh! a fraction of a second behind!

Re: problems between cable modem and router
 

Done that a few times, but it's good to verify I'm not missing something there. I've left them off for quite a bit longer; the SURFboards, I'm told, usually need more time. I'll give it another go to see if it magically fixes itself.

thanks
--sg

Re: problems between cable modem and router
 

Operative word = "should"

I get my IP dynamically, but could they still pull the the MAC ID from my NIC through the modem? I'll check and see if that's the case.

thanks
--sg

Re: problems between cable modem and router
 

Finally found the problem. Buried in the router configuration was a little bit about the WAN connection speed. Dropped it from 100 mbps to 10 mbps and now everything goes smooth with a capital SMOO. I had no idea I needed to explicitly set one or the other; the router manual doesn't mention it at all. I only found it because I was randomly going through the config pages. Be ye warned...

Thanks everyone for your assistance
--sg

Re: problems between cable modem and router
 

Good Find! :)

Yes, many (especially older) cable/DSL modems are only 10Base-T (10Mbps) devices.

Re: problems between cable modem and router
 

Yep, the cable modem is second-hand and showing its age. I think it's the only component I'm using that isn't 10/100. Might have to "accidentally" drop it in the lake...

Re: problems between cable modem and router
 

i think this thread is done, but...

good advise; only thing i'd change is rather than give it time to warm up is DEFINITELY wait until the cable modem (cm) has block sync - solid green "Cable" light on some models; on most motorolas it's the "Online" light, which doesnt go solid unless the "Receive" and subsequently the "Send" lights go solid green.