configuring a wireless router with a DSL modem...

[jjoensuu]

Hi all,

I have been trying to get a wifi router (Linksys WRT54GL) configured to work with a DSL "modem" (Siemens Speedstream 4200) on my Optusnet account.

PPPoE is used on Optusnet to connect the DSL modem to their server.

The DSL modem has only one ethernet port. This would be used by the cable coming from Linksys. Linksys on the other hand has 4 ethernet ports for plugging in devices (and 1 for the cable to the DSL modem).

I have given the DSL modem the following configuration:
-Mode: NAPT (other modes: "Optus Bridge" and "Full bridge")
-IP address: 192.168.1.1
-IP net mask of 255.255.255.0
-default gateway setting of "Use WAN"

Also, the DHCP server functionality is enabled on the DSL modem, with following settings:
-start IP address: 192.168.1.2
-end IP address: 192.168.1.254
-IP net mask: 255.255.255.0
-default gateway: 192.168.1.1 (itself)
-DNS server: itself
-domain name: Test

Also, the NAT/NAPT settings are "NAPT only enabled", and no static routes are set.

With these settings, I can access the internet if I plug in my laptop to the single port on the back.

However, I have not been able to get Linksys to work with it. I have set Linksys with following settings:
[SETUP > BASIC SETUP]
-Internet connection type: automatic configuration -DHCP
-Host name: blank
-Domain name: Test
-Local IP Address: 192.168.1.2
-Subnet Mask: 255.255.255.0
-DHCP Server: ENABLE
-Starting IP Address: 192.168.1.100

[SETUP > ADVANCED SETUP]
-Operating Mode: Router
-Dynamic Routing: Both (meaning: for LAN & Wireless, and WAN)
Static Routing: none set

I did not think it mattered that both routers are enabled as DHCP servers, since the Linksys is the only thing that can be connected to the DSL modem.

However, if connect Linksys to the DSL server and plug in my laptop to the back of Linksys, I have no access to the internet.

I had this working before but as the lazy bastard I am, I did not document the configuration.

Does anything look like it is misconfigured, missing, or unnecessary in these settings?

For example, should the DSL modem be set to work as a bridge of some sort, rather than in "NAT/NAPT" mode?

thanks,

JJ

 

[bcastner]

You have two DHCP servers, two devices specifying the same subnet scopy, and all the Gateways point to themselves.

This will never work.

. Set the Modem to Bridge Mode.

Connect the modem directly to your computer and access the Web based setup pages.

Set bridge as desribed on page 35 of the manual:

http://subscriber.communications.siemens.com/documents/4x00UG_English.pdf

. Let the Router handle PPoE authentication and translation. Let the router handle DHCP.

Connect the Linksys directly to your computer. Access its web-based setup page.

Set on the first page the connection type as PPoE. A page will open to allow you to enter your ISP authentication information. Enter this information and save the page.

Reconnect workstation to router. Reconnect modem to router on the WAN port of the router.

Power off everything. Turn on modem, and when stable turn on router. Then turn on workstations.

 

[jjoensuu]

thanks bcastner,

your instructions did help to resolve the issue. I was avoiding to set the DSL modem as a bridge because I "remembered" that I used to be able to access both the DSL modem web-interface and the Linksys web-interface at the same time. Do you know of any form of setup that could make that possible?

Also, a few questions about your statement "You have two DHCP servers, two devices specifying the same subnet copy, and all the Gateways point to themselves":
1. why is it a problem that both are DHCP servers, considering that the DSL modem only has one input and it is the Linksys that is plugged in it?
2. how can they see each other if they specify different subnets?
3. I did not see a setting in Linksys to specify a gateway; does it become a gateway automatically when it is specified as a DHCP server?

thanks for your help

 

[bcastner]

Q1: why is it a problem that both are DHCP servers?

A: Because they have have routes on the same subnet. As you discovered it did not work, because when a client sends out its broadcast to find a DHCP server it gets two responses. It takes whatever reaches it first and does direct TCP/IP addressing to the DHCP server from that point on.

What happens is that you end up with clients with different Gateway addresses, and the possility (because the DHCP scopes overlap) of having two clients with the same IP.

Q2: how can they see each other if they specify different subnets?

A: They were not on different subnets. Look at your subnet masks above.

Q3: I did not see a setting in Linksys to specify a gateway...

A: Its a router]/b] The router has one foot (IP) on the LAN side, and one foot (IP) on the WAN or public internet side. And the intelligence to decide which of these two Gateway points to use to pass traffic.

.

 

[bcastner]

I forgot. Apologies:

your instructions did help to resolve the issue. I was avoiding to set the DSL modem as a bridge because I "remembered" that I used to be able to access both the DSL modem web-interface and the Linksys web-interface at the same time. Do you know of any form of setup that could make that possible?

A: When the modem is in "Bridge Mode" there is nothing to configure. No IP concerns, no server concerns, no firewall issues. Nothing.

Your only configurable device is the router. And that is all you need.

Having said that, there are modems that offer VLAN features where you could bridge the modem portion to VLAN 0, and use another VLAN to access it.

If your modem is a native Universal Plug and Play device and you have UPnP enabled as a service on your computer, and a Firewall exception made for UPnP, you might be lucky and have it appear in Network Neighborhood.

It would appear in Vista, but that is another story.

.

 

[jjoensuu]

hi bcastner,

and thanks again. So it looks like the only way this can work is when one of them is setup as a bridge and the other one as a router.

Also, in the subnet question (Q2) I actually meant that I had put them onto the same subnet for the reason that they would otherwise not see each other. For that reason I thought that the only way to get them to work together was to have them on the same subnet. But in your initial reply you indicated that it would not work, and I wanted to know why not. In any case, the answer you now gave to Q1 also explains this.

cheers

 

[bcastner]

Glad you got it sorted.

Best.

Bill