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Modem-router + external cable modem = no Internet

Last response: in Networking
May 28, 2007 12:19:26 PM

Hi, I just spent the last hour trying to find help in what's been posted already and didn't find anything I could use, so here I am opening a new thread, apologies if the question's been answered in the past.

My problem: I just switched to cable with Virgin Media (ex NTL/Telewest), but didn't think (yeah I know) that my wireless modem router, a Linksys WAG354G, would have a problem with handing the Internet connection over to an external modem. I tried my luck with Virgin support (pretty helpless) and Linksys (very good feedback but still no solution).

So I can connect my laptop to the cable modem through the router but only when setting this one to bridge mode, problem is, I can only get one IP address and therefore connect one PC at a time. So far I gather that my modem-router won't work with an external modem...

The obvious solutions are either switching to ADSL through a landline (not going to happen anytime soon) or replacing my still new-ish modem-router for a plain "broadband" router, but I really don't feel like getting rid of my WAG354G just yet.
The guys at Linksys also told me when I asked them that I "might" get my router to work with the cable modem by adding a plain router between the two and hooking up the two routers together. But they couldn't give me a firm answer...

So in short: can I add a "cheap" broadband router behind the cable modem to link it to my existing modem-router (and wireless network beyond)? Would a switch do the job? Or is it better to replace the modem-router with a broadband router?

Many, many thanks in advance...
May 28, 2007 10:09:37 PM

First, there's no reason for the Linksys to not work with the cable modem unless your cable provider uses some obscure way to allow PC's to connect (some use L2TP, which few routers support). If the offer basic PPPoE connections the Linksys should work just fine.

It will work with an intermediate router if, and only if it has support for the type of connection they offer, but you need to find out exactly how they set up connections, which protocol they use (and I don't mean TCP/IP). You do need to make sure you know some routing basics to configure the intermediate router as well.
May 29, 2007 10:47:04 AM

I don't know what standard my ISP (Virgin Media, ex NTL/Telewest) uses, but if I understand right, my router won't route any Internet traffic by itself, because of the built-in modem...

Here's an article I've found about it.

I don't really understand that the manufacturers didn't think about implementing a software option somewhere to deactivate the built-in modem. If it can do the most complex things, it should be able to do the simpler ones, with the right software...

Tonight I'll try setting a PPPoE configuration, using my ISP's DHCP & DNS servers, and the modem as the default gateway.
Related resources
May 29, 2007 11:23:09 AM

You're SOL. You can't use a DSL Modem/Router on a cable system. PPPoE only works on DSL. Get a cheap wired router, Disable DHCP on the Linksys and you can use it as a wireless access point.

May 31, 2007 6:05:34 PM

DSL is PPPoA, while cable is usually PPPoE. The cablemodem is usually DOCSIS and has nothing to do with IP.
But the WAG345G is a modem+ruoter (I read it as router earlier), the WAN port is not ethernet but DSL. In that case it will not work as the WAN port isn't ethernet, and an intermediate router won't work either. You need another router to do what you want, I'm afraid, or follow Grumpy's suggestion and use the WAG as an WLAN AP.
May 31, 2007 11:56:41 PM

Here in the States, DSL is PPPoE and Cable is DHCP though that's the way DSL is moving as well.

June 1, 2007 8:36:37 PM

I can't say how it is in the states, so I'll take your word for it :) 
Either way we can agree that the OP's WAG won't work with cable.
June 8, 2007 6:57:04 PM

this is a good reason not to by an all-in-one unit.