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I have a modem thats 10yrs old. The adapter broke, and my ISP sent me a new modem which disconnected every time the phone rang. I told my ISP about it, and they sent me the same model with the same problem, so I just used the AC adapter and it works.

But I think I should get a new one. I don't want the problem mention above. I have a good router, so I don't need a modem/router in one. I am using DSL with no plans on using cable.

What should I know about modems before buying one? I have seen a modem online with a http gui which confuses me. Why would i ever need to see it? My router is a pretty solid with features and stats. Do modems affect IPv6? I see mentions of ADSL2, does that mean anything?

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Do you have a DSL filter on your phone line? This may be able to prevent the disconnects when the phone rings. – music2myear Aug 9 '11 at 21:46
If the phone frequency is not properly filtered from the DSL frequency, your splitter might be the culprit. – karatedog Aug 9 '11 at 21:46
@music2myear everything is properly filtered hence why my old/current one is stable – acidzombie24 Aug 9 '11 at 23:16
What is the current setup? The 10-year modem with the new AC adapter? What is the manufacturer and model number of these modems? Are you positive that the replacement(s) are the same model/version as the decade old modem? At the xDSL company I used to work at, new versions were designed every 3 years. – sawdust Aug 10 '11 at 1:38
@sawdust: I'm to lazy to actually look but the two replacements were about a month apart and were not the same model (maybe not even same brand) as the older solid modom. – acidzombie24 Aug 10 '11 at 2:16

It's possible that your phone is to blame for the hangup on phone ring. DSL operates using sub-audible signals over your phone line. If your phone is old or poorly made, it may emit signals in the general range of the DSL modem. Putting DSL filters between your phone and the line may help prevent this interference.

Regarding DSL modems, I've found the 2Wire brand devices work exceptionally well. But they only work for AT&T connections. My dad worked for AT&T (well, first it was Pacific Bell, then Southwestern Bell...) for many years, and for the last several years he was the DSL installer for our area. We always had the 2Wire devices (which are usually the more expensive options you purchase from AT&T. Around $100 for the device. It replaces most routers as well though because the 2Wire, in addition to being a DSL modem is also a 4- or 5-port network switch and a wireless router.

You don't usually interact with the control gui of the modem. An HTTP gui just means that in the case you need to set up your wireless or manage a more complex firewall option, you'd log into a page hosted on the modem itself to make these changes. They're generally as easy to use as an online banking page, in my experience.

ADSL2 is a collection of technology standards that allow higher throughput speeds on DSL. DSL is really the slow child of high-speed internet. Some of this is due to the fact that it usually has to run over old copper lines which were meant for analog telephone signals, not digital data signals. ADSL2 is supposed to help bring it into a more competitive system by at least addressing the protocol standards and such.

If you're on an old copper connection, you may want to look into an ADSL2 modem. But if it costs a lot more, I would not consider it enough of a requirement to pay a premium for it. More of an "it's nice if the device has it, but not a problem if it doesn't" sort of factor.

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As far as why you'd need a gui...

Your modem has settings, and you may need to configure it. You can either telnet to it, or have an http interface to it. Obviously an http gui is easier for most people.

In general there are two main modes you can put your DSL modem into. One has the modem connect to your phone company on one end, and have an ethernet TCP/IP network with DHCP on the other, usually a nonrouting one (e.g. 192.168.x.x, 10.x.x.x...). You may need to authenticate to your provider through the modem, with a web browser and the http gui. You may also want to configure the TCP/IP network it creates, http gui is the easiest way. Now, once you hook your router to this, you create a second network. Now you need to configure the second network, and worry about a double NAT.

You can also change your modem to bridge mode, where the modem becomes a dumb pipe, and your router now runs PPPoE over the dumb(er) modem, and you just have the one network, the one NAT.

This is what I did when I had DSL, I did the double network thing for a bit, then I put the modem into bridge mode and used the router for everything.

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For people in Europe, the answer is going to be slightly different. The ADSL network is subtly different, which means US modems won't just work in Europe. Newer modems can probably be switched.

The first thing you absolutely need to know in Europe is whether you have ISDN. (It's far more common in Europe than in the US). ISDN allows for 2 simultaneous phone conversations, which means that ADSL for ISDN must avoid both those channels. If you have ISDN, you'll need an "Annex B" ADSL modem. If not, you'll need an "Annex A" ADSL modem.

"Classic" ADSL is already a decade old, and has speed limits. More than 8 Mb is flat-out impossible, even in the best of situations. However, technology doesn't stand still, and ADSL2 is widely available. If your ISP/telco offer it, an ADSL2 modem can achieve up to 12 Mb. And with ADSL2+ (the latest ADSL variant) even 20Mb/s is possible. Instead of looking at those ADSL version numbers, it's often easier to look at the speeds offered. Your modem and your ISP will both be advertised with their best speeds; your connection speed will be limited by the lowest of the two (and possibly phone line quality, as usual with ADSL everywhere).

Since you already have your router, you can run your DSL modem in "bridge mode". In this mode, the modem will accept packets from one source only (your router) and send the to your ISP, and vice versa. This is a simple mode of operation and rather robust as a result.

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