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How to configure a DSL modem for connection to a router

Posted on 2004-09-03
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I'm trying to configure a DLink DSL-300T adsl modem with one ethernet port for connecting to the WAN port of a DLink DI-624+ wireless router. The broadband connection works fine without the router inline, and connecting to a hub which connects to 2 PC's. I think with the router inline I need to somehow pass-through the IP address assigned by the ISP to the router. I've tried the following setups without success.

Setup 1

Modem:
ip=192.168.1.1
subnet=255.255.255.0
DHCP=dissabled

Router:
ip=192.168.1.2
subnet=255.255.255.0
DHCP=enabled
WAN=static ip 192.168.1.1

PCs: default gateway=192.168.1.1


Setup 2:
Modem: set to bridged mode
Router: WAN set to dynamic ip
PCs: default gateway=192.168.1.2

Setup 3:
Modem: set back to PPP0A mode
Router: WAN set to static with ip 192.168.1.2

Setup 4:
Router: changed static WAN ip to 192.168.1.1


Most helpful article I've found so far was at http://www.zensupport.co.uk/forum/shwmessage.aspx?forumid=26&messageid=228 however I notice I haven't followed it exactly because in the thread the LAN addresses are 192.168.0.x rather than 192.168.1.x .

I'm hoping to talk to someone on here with some practical router setup experience, I'm not looking for lots of url links to more reading matter please.
 
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Question by:ncw
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by:fixnix
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if you're having the modem be 192.168.1.1, then the router should have (on the wan) 192.168.1.2 (or other address in the 192.168.1.x subnet)

Default gateway on the router should be 192.168.1.1

LAN side of the router will be a different subnet (like 192.168.2.1, netmask 255.255.255.0)

Client computers can get their IP via DHCP from the router or use 192.168.2.x for an IP, 255.255.255.0 subnet, and 192.168.2.1 for the gate way if that is the IP assigned to the LAN side of the router)
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by:fixnix
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Alternatively, set the modem as follows:

Modem:
ip=192.168.1.1
subnet=255.255.255.0
DHCP=enabled

Router, wan side: use DHCP for IP, subnet, DNS
LAN IP= 192.168.2.1
LAN netmask= 255.255.255.0

and enable DHCP on the LAN side and dish out addresses from 192.168.2.2-192.168.2.20 (or 50 or whatever)

and enable DHCP on the client computers.
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by:ncw
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fixnix: I'll try the first option first. Are you saying that the LAN can be or MUST be on a different subnet?
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by:fixnix
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Must.  If you use the WAN and LAN sides of a router, then they must be on different subnets.

FWIW, you can use a router as only a switch or hub by just using the LAN side.
If you want it to pass traffic to the WAN side then they must have different subnets.

The subnet  is how the router determines if a packet should stay on the LAN side, stay on the WAN side, or cross from one side to the other.
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by:rid
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Generally, the router acts like it were a PC on the inside of the modem. So, accordingly, if you have dynamic IP from your ISP, the router must be set to use DHCP for getting its IP from your ISP, via the modem. If you have static IP, you have to adjust the router for that kind of setup. All values should be given to you from your ISP.

Your LAN, the inside of the router, is a private subnet. You can choose whichever private net IP range you wish, but if the router is preset to 192.168.1.1, why not use that subnet....  There is no benefit in wrestling with the router here. A private IP range is a private IP range. Unless you have too many PC's, keep it simple.

If your router can be a DHCP server for the LAN, you can set all PC's to obtain IP automatically, if you want it that way.

/RID
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by:fixnix
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rid: I gathered from the original post and configuration that the modem gives private IP's on it's internal side and it was set at 192.168.1.x.  Therefore, adding a router downstream would require a different subnet.  If ncw wanted to use the same subnet on everything, his router wouldn't be in use as a router but rather a hub and the WAN port would just  be empty and he'd have the same setup as he said worked with just the modem and a hub.

"The broadband connection works fine without the router inline, and connecting to a hub which connects to 2 PC's." brings up an obvious question though....why do you need an extra router in line?  I answered how to configure the router since that is what the original question was, but I can't think of a reason offhand why you'd want a router in between the LAN and the modem.  Is there a reason you don't just stay with the hub since you said everything worked that way?
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by:fixnix
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Basically the modem is already acting as a router.  I have a similar setup at our office where I run additional routers after the first one, and it makes sense here.  I split the main broadband connection's router to an additional router for each tenant in our building.  That way each company has their own subnet isolated from everyone else's.  If a 4th floor company employee brings in a laptop with a virus that attacks their LAN, the rest of the companies aren't affected except for possibly less bandwidth available to the internet if the attack is going to the outside world.
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by:rid
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OK, so it's a modem + router combo. Sorry, didn't notice. It doesn't make much difference other than make yet another router redundant in this case... Go for the subnet that the modem+router uses and use the other box as a switch.
/RID
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by:fixnix
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Actually, I gathered it to be 2 separate pieces.

from "I'm trying to configure a DLink DSL-300T adsl modem with one ethernet port for connecting to the WAN port of a DLink DI-624+ wireless router."

I assumed the following:

1:  Modem.  Which also acts as a router but has only one port.
2:  Router.  The DLink which is probably 4 port and what the PC's will connect to.

--------

Now I just noticed he stated it is a wireless router.  Perhaps that is the only reason for adding this router...the wireless fuature.

If that is the case, you can safely ignore all together the WAN port and:

1.  Configure the DLink to a LAN address of 192.168.1.1 (default I believe)

2.  Connect the modem to the LAN side of the DLink (if it does not link, then you will need a crossover cable)

3.  *IF* the modem/1 port router has a DHCP server, then Configure the DLink to *NOT* be a DHCP server
       If the modem does not have a DHCP server then configure the DLink to be a DHCP server serving the same subnet:  192.168.1.2-192.168.1.20 (or to 254, but you're not going to have 254 pc's connected so no reason to fill up the entire range...nice to leave room for static IP's if needed)

4.  use normal patch cables from the other PC's to the LAN side of the DLink, and configure your wireless access as per the DLink manual and your wireless clients' documentation.

Let us know if you get stuck anywhere, I don't get email notifications of new posts when away from the office, but I try to keep a "manual" weekend watch on threads I'm posting on.
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by:fixnix
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Oops...just realized both are DLinks.  Sorry...in my last post, assume every instance of "the DLink" is refering to the "DLink DI-624+ wireless router"
and all instances of "modem" and "modem/1 port router" to be the "DLink DSL-300T adsl modem"
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by:fixnix
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I'm tempted to post a question in the Misc section.....

"Why is it so hard to read...and actually see the details...on Fridays?"

I've had a few brain farts today.
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by:ncw
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fixnix: Yes one reason for a separate router is that it is wireless and I may want to locate it remotely in the roof space, but also it is 4-port and I want to use it to share broadband with my neighbour - so that's a good reason to use different subnets which I assume wouldn't work if I plugged in the modem into the WAN side of the router; or do I then need another router (I think the answer is yes). I may get rid of the hub depending on the location I choose for the router. Also I believe there are additional features available with the router.

So unless you advise otherwise, I'm thinking that the best arrangement is:
1. modem connects to WAN port on router
2. modem DHCP  = dissabled
3. router WAN = dynamic PPPoA
3. router LAN DHCP = enabled
4. router default gateway = 192.168.1.1
4. router ip = 192.168.2.1 subnet mask 255.255.255.0
5. LAN ip range = 192.168.2.2 to 192.168.2.x subnet mask 255.255.255.0
6. Client PC ips either obtained automatically or fixed as 192.168.2.2+

Have I missed anything?




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by:emeraldv45
emeraldv45 earned 50 total points
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modem
IP:192.168.1.1
Mask:255.255.255.0
DHCP:disabled

Router
WANIP:192.168.1.2
WANGATEWAY:192.168.1.1
InternalIP:192.168.0.1
InternalGATEWAY:192.168.0.1
DCHP:enabled

You must use different subnets for the link between the modem and router and the internal network.
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by:emeraldv45
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modem
IP:192.168.1.1
Mask:255.255.255.0
DHCP:enabled

Router
WANIP:DHCP
InternalIP:192.168.0.1
InternalGATEWAY:192.168.0.1
DCHP:enabled

would also work
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by:fixnix
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Okay...couple of issues here:

Separating the wireless subnet for the neighbor is a good idea.

Are you planning to use wireless clients in your house as well?  If so, you would need a wireless access point on your LAN which would all be on the 1992.168.1.x subnet and your neighbor would be on the 192.168.2.x subnet from the current DLink wireless router.

If you are hardwired in the house, then I would keep your hub and have everything in your house on a 192.168.1.x LAN, and use the wireless router only for the wireless neighbor's access.

In that scenario, here's the network map:
{ISP}------

-------<wnatever IP the ISP assigned>{modem}<192.168.1.1 (the LAN port on the modem)>----crossover cable here to hub----

----{hub}------

---------{all client computers in your house hardwired and also one patch cable going to the WAN port of the wireless router}----

----<192.168.1.2>{WAN side of wireless router}<192.168.2.1 (LAN side of wireless router, DHCP server enabled)>------

-----neighbor's wireless clients


Hope that is somewhat clear.  Will need a little more info on the modem.

You don't need PPPoE on the wireless router.  You may be using PPPoE on the modem on the ISP (WAN) side, but that's the only place.  Once you have a ethernet cable coming out of the modem to your LAN, everything is just straight TCP/IP.

I'll be here tonight and all weekend, and this is not a complicated setup so I'm sure we can get you hooked up and overcome any obsticles along the way.  Your 2 step 4's above will actually break the network because it's using itself (on the LAN side) as a gateway...so packets have nowhere to go.
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by:fixnix
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and emerald is correct in his/her post as well....just a matter of how and if you want to divide your neighbor into a separate subnet.  I could go on a long windy rampage about wireless security as well.  If your neighbor gets compromised and winds up running a kiddieporn site or spewing millions of spam messages per day without his knowledge, all that crap is going through *your* connection and you could have to defend any legal issues...not a lot of precedences set in that area yet, with some going for and against the broadband subscriber.  Even winning a case is still a loss of time, effort, and legal expenses.  Anyway...you're in the right place to get everything working :).
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by:ncw
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I need to read through this again and test the settings. The PC's inside the house will be hardwired, but I might want to use a Laptop inside or in the garden wirelessly. Can two subnets not connect wirelessly to one router? As to security, I know WEP is not inpenatrable but I'm in the UK in the countryside rather than the city, so I don't feel too vulnerable. If necessary I could buy an access point dedicated to the neighbours connection.

Thanks very much for your help so far, I fell sure I will get something up and running either tonight or tomorrow.
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by:rid
rid earned 50 total points
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I think it is important to differentiate between modem and router here. If you get one IP (dynamic or otherwise) from your ISP, this is a public IP. If the modem includes a router, your connection to the modem ethernet connector is a connection to a router's LAN connection, which will be an IP on a private range. Several PC's can use this IP as their default gateway to the internet, and they need to connect through a hub or switch. The setup of the router (modem, in this case) LAN side must reflect your needs (DHCP or not etc) for your LAN. If the modem does NOT include a router, the story is quite different.

If you want to create an additional subnet, this will probably have to be a subnet to your existing subnet, unless you have more than one public IP to use. I.e. you have to go one step further, as the "primary router" will probably not be able to have 2 IP's on one connection.

If the first subnet is 192.168.0 , I suppose you could get another router that will route between this subnet to the next, for instance 192.168.1 .

The actual benefits of such a setup escapes me, even if you're about to let your neighbour in to share the internet.

The easiest way may be to disable routing in the modem and use the more capable (wireless + 4 port) router for all PC's involved.
/RID
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by:fixnix
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Let us know if you get stuck.  That wireless router can only have one subnet on the LAN side.  If you connected to the wireless network, you'd be on the network with your neighbor.  You'd have internet access but could not share files with your desktops....only your neighbors haha.   If you don't share folders or printers, you could firewall your LAN boxes to only accept traffic from the gateway IP and no outgoing packets to anything on your subnet except the gateway.  At that point you could just allow your neighbor on the same subnet as you and just use the wireless router as a hub and access point.  Throw everyone on 192.168.1.x or whatever subnet the modem's LAN side IP is in.
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by:holger12345
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Hi, there's written a lot... but i really didn't got, how the wireless router (I'll call it "WL" below) and the adsl modem ("MOD") are connected.. So I'll draw a graphic:

WAN-to-ISP        Eth0      Eth0         Eth1
                _____                   _____                   _____                
------------| MOD|-------------| WL   |-------------| HUB  |-----PC1
                --------                 --------                  --------                
                                                                            |______PC2

That's the only way it makes sense (but not at all). Why aren't you connecting the WAN-Port of the WireLess to the ISP? The MODem isn't neccessary as it has no proper use in this configuration (only that you used it before!). Your WireLess Router IS in fact IS a modem with the extra function of having an integrated switch to 4(?) LAN-ports an a wireless access point (also connecting to the LAN).
The only thing you can't do with the wireless router is to let the PCs terminate the PPPoE-connection. The router in general is a terminating equipement - and it doesnt make sense any other way cause only ONE end point can be set to the PPPoE (Point-to-Point = ISP-to-You)connections

So I would setup the following

WAN-to-ISP        Eth0      
                _____                   _____                          
------------| WL   |-------------| HUB  |-----PC1
                --------                 --------                
                                                |______PC2

regards, Holger

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by:ncw
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holger12345: I understood that it is the DLink DSL-604T which includes a modem - there's no place to enter adsl connection details in the setup for the DI-624+.

Proposed config:

                                           DHCP server
              WAN: ISP IP           WAN:192.168.1.2
              LAN:192.168.1.1     LAN:192.168.2.1
                _____                   _____                   _____                
------------| MOD|-------------| WR   |-------------| HUB  |-----PC1 192.168.2.2
                --------                 --------                  --------                
                                               |                            |______PC2 192.168.2.3
                                               |
                                               |___/\/\/\___/\/\/\________PC Neighbour 192.168.2.4

Or:

                                           DHCP server
              WAN: ISP IP           WAN:192.168.1.2
              LAN:192.168.1.1     LAN:192.168.2.1
                _____                   _____                   _____                
------------| MOD|-------------| WR   |-------------| HUB  |-----PC1 192.168.2.2
                --------                 --------                  --------                
                                             |   |                        |______PC2 192.168.2.3
                                             |   |
                                             |   |_____/\/\/\___/\/\/\____Laptop 192.168.2.4
                                             |
                                           _|__
                                          | WR |___/\/\/\___/\/\/\____PC Neighbour 192.168.3.2
                                           ------
                                     WAN:192.168.2.1
                                     LAN:192.168.3.1

~ A picture paints a thousand words ~
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by:fixnix
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I'd go:



                                           DHCP server
              WAN: ISP IP           WAN:192.168.1.2
              LAN:192.168.1.1     LAN:192.168.2.1
                _____                   _____                   _____                
------------| MOD|-------------| HUB  |-------------| LAN   |-----PC1 192.168.1.2
                --------                 --------                  --------                
                                             |                           |______PC2 192.168.1.3
                                             |  
                                             |  
                                             |
                                           _|__
                                          | WR |___/\/\/\___/\/\/\____PC Neighbour 192.168.2.2
                                           ------
                                     WAN:192.168.2.1
                                     LAN:192.168.3.1

and use the wireless on your laptiop on the neighbor's network if you didn't need filesharing on your LAN for the laptop.
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fixnix earned 350 total points
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Oops...musta posted that one too laste into the partynight....no WAN on the hub haha...should have been:

 I'd go:



              DHCP Server          
              WAN: ISP IP          
              LAN:192.168.1.1    
                _____                   _____                   _____                
------------| MOD|-------------| HUB  |-------------| LAN   |-----PC1 192.168.1.2
                --------                 --------                  --------                
                                             |                           |______PC2 192.168.1.3
                                             |  
                                             |  
                                             |
                                           _|__
                                          | WR |___/\/\/\___/\/\/\____PC Neighbour 192.168.2.2
                                           ------
                                     WAN:192.168.1.2
                                     LAN:192.168.2.1
                                     DHCP Server

and use the wireless on your laptiop on the neighbor's network if you didn't need filesharing on your LAN for the laptop.
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by:ncw
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I've not been able to progress this today, can't seem to access the internet using adsl so I'm back to dialup. This happened since disconnecting my adsl modem to temporarily change the splitter, and since using the dialup connection too.

I can ping modem but not to the outside world
Gateway and DNS are correct in network tcp/ip properties
rebooted PC
In the modem admin Modem status is connected

I've tried a ping test from the modem admin page and it says 'network unreachable', I pinged 217.12.3.11 which is www.yahoo.com and pings ok over dialup. The modem test is ok and status says connected.

Even reset modem and re-entered details.

Huh .... always some problem!
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by:ncw
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Fantastic! Easy when you know how, when you've had a lot of help from your friends at EE.

Can we still offer extra points here by posting questions just to offer points to individual experts?
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by:fixnix
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So I assume you're all working now? great!  As far as the posting a question for the sole purpose of giving more points to someone, I believe that is not allowed.  Glad we could help tho!
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by:ncw
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Thanks everyone!
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by:ncw
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