I tried to google this but all I get are explanations of the differences between a router and a modem 
Anyway, I have a DSL modem plus router combo where the modem is not functioning properly but the wifi router is fine. I want to purchase a new modem-only unit and then use just the wifi/router part of the existing modem+router unit. Is that possible ? How do I configure the modem+router to function as only a router ? The existing router is a TP-Link (model td-w8961nd).
thanks !
All things are possible, but it may take quite a bit of messing about.
The trouble is that even just saying “router” doesn’t get you the full story. There is typically a lot going on in a combined WiFi-router-modem. It tends to all work most easily when it is all in the one unit. When you get more than one device, you discover that both devices want to control a lot of the under-the-hood stuff, and you get into trouble.
No matter what, a modem will contain routing functions, and will always do so. It is the modem that controls the passing of packets between your ISP’s network (the WAN) and your home network (the LAN). That involves the lion’s share of the routing activity. And it isn’t simple.
The WiFi element does also involve routing, but only within your home network, and the largest part of that may well be just getting the packets to and from the modem. But it also involves talking to the printer, file server and the like.
The easy answer is likely to be to shut down essentially all functions on the old WiFi-router except for basic WiFi capability, and point it at the new modem for everything else. This means disabling the DHCP service. It should find the DHCP service on the new modem, and use that, and from then on the system should all work OK. If you use WiFi address filtering and the like to improve security, these stay on the WiFi device. But allocation of local network addresses, and the distribution of other network information (DNS server etc) come from the new modem.
Here is the manual.
If the new modem is just a modem, I would think you would be okay just plugging it into the router. That is how I set up with the modem I bought for Comcast and a wireless router.
Not going to work, I think.
typical home router (no DSL) has WAN ETHERNET port out to connect to DSL modem or cable modem, and the 4 LAN (local) Ethernet ports.
You box indicates the WAN port is actually not Ethernet WAN but DSL. There is no way to connect any Ethernet WAN from the old device to the “Ethernet out” of the new DSL modem. (Your new DSL modem will have DSL in from the world, Ethernet out to your router/firewall/single PC). At the very basic level, it is RJ11 (phone) not RJ45 (Ethernet) socket. Wiring is for a phone line.
you could turn it into another network switch - just disable DHCP and it won’t hand out addresses claiming that it is the gateway address.
I’m not sure it’s flexible enough to use any of the 4 local ports as the WAN address - it seems they are all bridged together.
Plus, with a DSL router/modem - as the manual indicates - the router does the DSL PPPoE login. With a very simple only-DSL-modem your PC or second modem has to do the DSL login. Additional issue.
Really, I would buy a replacement modem/router. As others allude, getting the existing router to work well with the modem can require changing the router settings for things like DHCP. I had a ADSL modem/router that I wanted to use with a fibre gateway (a modem for fibre), so it needed to just use the router function. Very hard to get it to work well with the fibre modem as they both wanted to be the DHCP server and the configuration was not easily changed.
And I would go further and buy a separate modem and router. Over the past 6 years I am on my fourth router and second DSL modem. I’ll be getting a third modem soon as they increased the speed to my area and my current modem is not capable. I’ve had 2 routers get flaky and need replacement. They work as secondary switches though. I’d hate to think having to pay for and configure a replacement combo unit seven times.
The “advanced setup - routing” page appears to indicate that you can specify something other than the inteernal ADSL modem as the gateway. So it appears that you can just connect a smart modem to one of the 4 ehternet ports.
Buy a modem. Put the login information into the new modem. Plug the new modem into one of the ethernet ports. Configure the old router to use the new modem as gateway for all routes.
but the typical plain old modem does not usually take the login information - it presents a PPPoE interface, and what connects to it - a router or a PC - must do the PPPoE login. It also typically does not do the NAT translation.
PPPoE is the protocol that goes over DSL. It usually requires you to login to get a valid connection, then gives you your IP address. Think of it like the super-high-speed version of the old dial-up modems from a network perspective.
Adding routes to your lame router simply tells traffic to try another IP address to get to the internet. It doesn’t solve the firewall and NAT issues.
NAT at a firewall/router takes internal addresses on the inside and translates them all to the one single outside, real internet address the phone company (or cable, or…) gives you. The NAT process also routes replies from the internet to whichever of the devices from your inside network started that particular conversation (or if you want a public server inside). It is how you can have multiple PC’s using one internet connection. Usually, on small home networks, the router is the DHCP server too, handing out internal addresses (and also telling where the gateway is).
As I said, the only thing I see the problem router as good for is to turn off all DHCP and use it as a switch. If the Wi-Fi is also enabled, it can be an AP, an “Access Point” connecting Wi-Fi devices to your wired network and the internet.
however, cheap fully functional routers are available in the $30-$40 range, so why even bother trying to salvage this?
(There is a complex configuration involving using the CP to make the PPPoE connection and running the necessary programs to be firewall, router, DHCP server to a simple DSL modem - but this is an additional complexity level.)
This. It is not as hard as others are making it out to be. Most modem/routers will function just fine as a normal router with a bit of setup. The only reason I could even think it might not work is if your ISP really locked it down, and you can’t replace the firmware.
I’ve never had a router from an ISP that did that, however. They are usually cagey about how to get into the configuration settings, but you can usually find out online, including the password.
The only thing that gives me pause is whether the “modem-only unit” will actually be cheaper than just getting a full router. Sure, if you forego Wi-fi, it may be cheaper. But most modems seem to be combo units now.
If the modem/router doesn’t have a WAN port in, it can’t be used as a router alone. Connecting a modem to one of the router ports will simply turn the back end of the router into a switch, and there will be no router/firewall/security functions at all.
I’d buy a decent new router to go with the separate modem. Combined shit is always weak at some point and far less flexible as needs change.
No, not this.
A “modem” simply translates DSL on a telephone line to DSL packets on an Ethernet wire. Unless technology has changed since I last dealt with plain modems, in the last 5 years, a DSL modem does not do login, nor NAT, nor DHCP, nor firewall. If it did, it would be a DSL router like the half-dead item under discussion. Something else, a PC or a router, has to do all those functions. (You do NOT want to try setting up a PC as a router/firewall…)
And that is precisely what modems are for. Your typical home router has a WAN Ethernet out - a port designed to connect to the internet - but it is for Ethernet, not telephone wire. Most home routers will do PPPoE (DSL) logins and talk PPPoE over the WAN port as a setup option connecting to a DSL modem; or they will talk plain Ethernet for cable modems.
If you have a slightly fancier router, or commercial grade router, have extra functions you need to do with your router, etc. - you want a plain DSL modem and let the router do the firewall/router stuff. The alternative - since phone companies seem to delight in delivering full DSL routers today instead of modems - is to put the phone company’s DSL router in “passthrough mode”; but now all traffic is double - NAT’ed.
In fact, I bet it’s almost impossible to get a real modem any more. A quick perusal of Best Buy finds “modems” are actually home routers.
Basically, on one side of the router is a single internet connection, with an external IP address. On the other side, is a private network with addresses like 192.168.x.x (or maybe 10.x.x.x). NAT translates those private addresses to the public address, and routes replies from the internet to the appropriate private address. DHCP hands out those private addresses, and also the gateway address - the IP of router (on the private side). Any internal packet not destined for the local network is sent to the gateway, which then NAT’s it and routes it to the internet.
The gateway - the path to the internet - is an addressed handed out by DHCP along with the IP address to any internal device. To use the dead router as a switch, TURN OFF DHCP. Then, wherever any internal device gets an address from, will also tell it the gateway address to get to the internet. Presumably that will be the new, real router firewall that is actually functioning as such.
the only bonus with the dead device is that it will bridge wired and wifi networks, so it can be turned into an “Access point” for your home network when connected to the wired network - if your home has spots your other wifi does not reach, or if you buy a new router without wifi…
Thanks for all the replies everyone.
My ISP does not lock me into any particular modem, so almost any DSL modem will work.
As mentioned above, a modem-only unit may not work for me and/or may be difficult to configure since I will have to use my old unit to do the DSL login (via some sort of pass-thru mode). Also, the price difference between a modem-only unit (yes, you can still get these although very few options), and a modem+router unit is only about $5.
And since the modem+router unit seems much easier to configure, I will go with that.
So, the plan is to configure the new modem+router unit nd turn off everything except wifi on the old unit. So which ports do I connect via Ethernet on my old and new units ?
Thanks for the info !
Won’t matter. On any of these units all the ports are essentially identical.
Yes, the technology has changed. The cheap ($20US) modems I have do DSL login. (Or can be configured for bridging).
Not to be picky, but that’s just not true. Specifically, this router doesn’t have a WAN port, but can be used as a router. It has a routing table, as shown in the documentation.