How to get access to the web interface of an ADSL modem running in bridge mode?

I have a D-Link DSL-2500U ADSL modem. Its default IP is 192.168.1.1 and default login/password for the web interface is admin/admin. If I plug in the Ethernet cable to the NIC of a computer (that runs Windows XP), assign the IP 192.168.1.2, then I can access the web interface at http://192.168.1.1 in the browser.

My modem is configured to work in bridge mode. If I also plug in the phone line that comes from the splitter and change the NIC settings on computer to obtain an IP addres automatically over DHCP, I get a real IP (and also a default gateway, which implies a default route) from my ISP. Everything is well, Internet works, except the fact that I can't access the web interface of the modem anymore, unless I unplug the phone line, restard the modem and change the NIC settings back as described above. I assume this happens because the IP packets for 192.168.1.1 destination go to the ISP gateway via the default route instead of going to the modem.

Until now I used to have ~8Mbps download, so I know for sure that my modem and my phone line can handle it. Recently my ISP raised the download speed up to 20Mbps, but I'm still getting only ~8 as before. I know I need to have ADSL2+ support. My modem supports it and this is enabled, I can see that in the web interface. But I would want to be able to access the web interface when the modem is running in bridging mode and my Internet connection is working, so I could see the maximum link speed, just in case that my ISP forgot to increase the speed on the DSLAM port.

How can I access the web interface in this scenario?

Solution 1:

When I am faced with a similar situation, I use either a Windows 2000 or Linux live CD in a virtual machine and set it to bridged mode. I set the IP to the same as the interface on the router and access the web interface that way.

The other was is simply to manually change my IP to match that of the router - as you shouldn't need to change settings to often, I do not really see this as that much hard work.

Lastly, unless you have a reason for setting it like this, you may want to enable NAT on the modem and use it as a full router for your network.

Solution 2:

Although windows will allow you to assign multiple IP addresses to one NIC, you can not do this if the NIC is using DHCP. Assuming you don't want to pay your ISP for a static address, then you have three choices.

1) Change you modem from bridge to NAT mode. - I am not sure why you think this should require any firewall changes on your PC. If necessary just set your PC as the DMZ machine on your modem.
2) Add a second physical NIC to your machine, one will connect to your modem, one to your access point.
3) Add a seperate router / NAT device between your modem, your PC and the access point.

I would suggest option 1. If necessary then I would buy a new modem/router that supports all the functions I require.

I don't think any of this has any bearing on your connection speed, or vice-versa.

EDIT: Sorry, I mis-understood your original post, it sounded like you had two seperate devices. With it being only one device, I can not see how you can connect to its interface while it is in bridged mode. And as others have said, there isn't going to be that much to configure anyway.
I don't think NAT is going to cause you any speed issues on a normal braodband connection. You are correct though, there is a maximum throughput that a home NAT device can handle, there are also several pretty good sites, like http://www.smallnetbuilder.com , that give throughput measurements for routers they test. Having said that, I expect your router would be able to handle 8 Mbs easy enough. There is also no gaurantee that your particular router is any faster when in bridged mode. Bear in mind its firmware will have probably been tested more for NAT mode than bridged because NAT is what they expect everyone to use.
As a last point, if you switch your router to NAT mode (and don't configure anything as DMZ) then it will do as a pretty good firewall for your PC, depending on your security requirements you could then turn off your software firewall which will ease the load on your PC's CPU.

I have a Netgear router running as a NAT device with 7 devices behind it (plus 2 smart phones sometimes), with most of them doing normal internet browsing or messenger or similarly low bandwidth use, speedtest still shows about 48Mbs down and 1.5 mbs up, I am on 50Mbs virgin broadband, so this is pretty much full speed.