|I have several of the same router, it was my first model, and several other D-Link ones.|
Your simplest solution is to just use the router all the time.
Your router has a hardware firewall - even with just default settings, you are much better protected from the bad guys when you connect to the internet through a router than when you connect directly connected to a network adapter .
That was the reason I got a router in the first place, although now I always have two or three computers connected to the router, or up to four when I'm working on other people's computers .
If you haven't changed the router's settings or reset them to defaults in it's configuration, or reset it to defaults externally (there's a tiny hole on the back near the power jack with Reset beside it - a slender pin or a stiff wire can be inserted there and held pressed in for x seconds to reset the settings to defaults) , it can't change any user setting automatically.
I'm assuming you have only one computer you connect to the router.
Have you changed which network adapter you're using on the computer, or are you using a different computer than before but not the same network adapter?
The only way I know of you could have the situation you have is your ISP requires MAC address registration, and you have changed which network adapter you are using.
Some ISPs require you register the MAC address of the network adapter or the router you connect to the high speed modem with in order to connect to their service. The MAC address is a unique identity code many network related devices have that can be detected by software. (The router calls it the MAC address; 2000 and XP call the MAC address the Physical address; 95, 98, 98SE, and probably ME call it the Adapter address.)
My ADSL ISP, Telus, allows up to two MAC addresses to be registered.
Other ISPs may only allow one.
When I run the ISP's installation software that came with my standalone high speed modem, one MAC address is automatically registered on a web site of the ISP's in the background .
1. one MAC address has been resistered.
In that case, the MAC address of your network adapter on the computer was CLONED, or typed in manually, in the router's configuration when it was set up. When the router is connected to the modem , the ISP's software can only detect whatever MAC address info the router provides. The router can either provide to the ISPs software it's own MAC address, or one you typed in that's a MAC address of a network adapter you have, or it can copy - CLONE - the MAC address of a single network adapter the router is connected to on the computer when you run the router's configuration.
In that case, whether you connect the modem to the router or the network adapter on the computer, your ISP sees the same MAC address.
E.g. in my case, when I first connected to my ISP I had no router, so the MAC address that was registered was that of the network adapter on my computer. When I later got a router, I CLONED that network adapter's MAC address in the router's configuration.
I can connect any computer to the router and connect to the internet because it has the MAC address of the original network adapter I connected to the ISP with, but I can only connect to the internet when that one network adapter is directly connected to the modem (or one other network adapter that I had registered).
If you changed your network adapter you're using on the computer, or you are using a different computer than before but not the same network adapter, the router would still be able to connect to the internet but not the network adapter on it's own.
2. Two MAC addresses were registered - one for the router, the other for the network adapter, but you have changed which network adapter you are using. In that case you can now only connect to the internet with the router.
If you have changed which network adapter you're using on the computer, or if you're using a different computer than before but not the same network adapter, if your situation is like mine, you could
- run the ISP's software installation when the modem is directly connected to the network adapter - that will register the MAC address of the network adapter.
- then run the router's configuration when the router is connected only to that same network adapter and CLONE the MAC address of the computer's network adapter in the router's configuration.
- both the network adapter alone and the router will then be able to connect to the internet.
If your situation is not like mine, I need to know the name of your ISP (Internet Service Provider) - e.g. you may have to go to a specific ISP's web site to change the MAC address registration.