|Are you trying to connect to it via a network cable connection and a wired network adapter, or via only a wireless network adapter? |
If via only a wireless network adapter......
The wireless network adapter must have it's software installed properly and be working properly in Windows - that doesn't necessarily include whether it can connect wirelessly to your router or combo router/modem, because the settings for that may not be correct, but it should be working properly otherwise.
The wireless network adapter's settings in Windows must be the same or compatible with the router's or router/modem's configuration settings in order for you to connect to the latter wirelessly.
If you can't connect to the router or combo/router modem wirelessly, you MUST connect to the router or router/modem by using a network cable between it and a wired network adapter on your computer, otherwise you can't access the router or router/modem device's configuration. All new wireless routers and combo router/modems I've seen came/come with a network cable, and all of the wireless ones I've seen have at least one wired network port, if not 4, or more.
The correct manual for the combo/router tells you what the default user name and password is.
Sometimes the router or combo router/modem has a user specified user name or password on it when you buy it used. The manual tells you where and how to reset the device to defaults without having to access it's configuration.
E.g. you insert a stiff wire in a hole in a certain place and press in an internal button in for x seconds while the device is powered, and is switched on if it has a switch.
- many of them have more than one possible version or revision - the manual should be the one for the version or revision you have, otherwise that info may be wrong
- some makers make similar but not the same model or version or revision for different regions, and the manual for those may state the default user name or password differently, and the default settings and what you see in the configuration can be very different, depending on the region it was made for (it has very different firmware).
- when the combo/router modem was provided along with an ISP's connection package, sometimes the firmware has been modified from default according to to ISPs wishes, and you need a different user name or password from that specified in the standard manual
- e.g. where I am, if that was provided by Telus, for at least one combo router/modem model I encountered, one of them was telus.
In that case, the ISP may have a downloadable manual on their site for the model that has their ISP specific user name or password in it, or ISP specific user instructions that tell you their defaut user name or password you're supposed to use for a model supplied by them.
- there is more than one type of DSL / ADSL modem or combo router modem. The type has to be compatible with what you need for your ISP - if it isn't, you can NEVER connect to the internet. ( I don't know if the same applies to cable - coax - modems. )
E.g. My ADSL ISP, Telus, upgraded their service - my original ADSL modem cannot work with the upgraded service - they provided me with a newer modem.
I have since obtained two used ADSL modems of the same model, different from the model and brand the ISP supplied me with - both work with the upgraded ADSL service.
If your ISP lists your specific used combo router/modem as compatible with their service, it should work fine. If they don't, email them or phone them, or contact the support site for the maker of it.
"a "garden wall" "
Do you mean a firewall?
That has nothing to do with the user name and password, in all the manuals I've seen.
The "hardware" firewall settings have defaults that work fine as is for most people, and you can modify them if you want to, but that only affects what is blocked or not blocked from passing through the devices network connection from the internet to the computer and operating system.
When you are connecting to the router's or combo router/modem's configuration you are not connecting to the internet - you can do that when the internet connection cable, e.g. the telephone line for ADSL service, is not connected to the combo router/modem. You should have no problem accessing the device's configuration if you use the correct user name and password (you may need to reset it to defaults externally).
NOTE: MAKE SURE the network cable is plugged in all the way into the ports on both ends of the connection, and that you're using a network cable that is not damaged (e.g. do it's end connectors latch in the ports so it can't come loose unless you squeeze the lever ?) , otherwise you may not be able to connect to it, or you may be able to connect to it but won't be able to get it to enter it's configuration.