Need to access my router

What router do you have? The most straight forward way is to check your computer's IP for it's "Default gateway". As long as your online, that should get you to your router. If it doesn't bring up a website, try pinging the IP. 

Also, most router GUI will be on port 80, but your browser should default to then when entering in a IP into the browser.

Last, off the top of my head, some other ones to try are 192.168.1.1 and 192.168.100.1 (some gateways).

My router is a Cisco from Cox, and was installed when the system was installed at my house.

As I indicated, I am using the default gateway IP address in the browser address box (e.g., http://192.168.0.1).  

This address pings just fine, but the browser times out and won’t bring up the Cisco admin GUI panel.

rbsorensen said:
My router is a Cisco from Cox,

I meant specifically what model router. Should be printed somewhere on it. 

rbsorensen said:
As I indicated, I am using the default gateway IP address in the browser address box

Actually you didn't indicate that, you said that was your "router's IP" not your PC's default gateway IP from IPconfig. What happens when you do a tracert to google? Start > Run > CMD > Tracert google.com

Almost seems like a phone gateway not registered for data, so the GUI is disabled, but that wouldn't let you online. Are you online via the device?

The router is the default gateway.   At least it is on my network.

Yes, of course it is

rbsorensen said:
Yes, of course it is

That response doesn't answer any of my questions. Sorry, I can't help without specifics. Maybe someone else will be able to communicate with you better. Good luck.

The default gateway and the router's internal network IP address have to be the same - they are, of course, both 192.168.0.1

Browsing on all machines works correctly and there are no problems with the TV either.  My only issue is trying to access the GUI setup on the router.

Navigating to "https://192.168.0.1" from inside my network should work, but it doesn't.

The Cisco model# is DPC 3825 - DOCSIS 3.0 Gateway

rbsorensen said:
The Cisco model# is DPC 3825 - DOCSIS 3.0 Gateway

Thank you. Is that the only device your using? No other routers or devices connected to it? The manual for the DPC3825 (page 26-27) says 192.168.0.1. If that isn't working, the only thing I can think of is something else on your network is using that IP or the device isn't functioning correctly. Have you ever been able to access the GUI?

There are no other routers and no IP address conflicts.  If there were conflicts I wouldn't be able to access the internet and post this response to you.

What I am thinking is that Cox possibly changes the router setup to block access after installation.

rbsorensen said:
 If there were conflicts I wouldn't be able to access the internet and post this response to you.

No, not quite. You can have IP conflicts and still route traffic in. It's the outbound HTTP request that isn't getting anywhere. 

rbsorensen said:
What I am thinking is that Cox possibly changes the router setup to block access after installation.

If so, that is the first time I have ever heard of that occurring, and it shouldn't be that way. Maybe try disconnecting the coaxial from the gateway, do a factory default, and see if you can access it that way? As long as they haven't messed with the firmware, then it should act as if it came out of the box. If the gateway works then, and then stops working after connecting the cable, then you know you are right. At that point I would ask a Cox moderator here, or call Cox, and ask why it's doing that. Or even swap it out for a different one.