What is the IP address of your Router? Open a Command Prompt as Admin and type
ipconfig /All and press Enter. The Default Gateway IP address will be the Routers IP address.
Unplug the Router and plug the modem directly into the computer. Do the Ipconfig /All command.
This should show the Default Gateway as the Modems IP Address.
The DNS server IP address should be the same as your Internet Service Providers IP Address or the Routers IP address.
You can also use Googles IP 8.8.8.8 Alt 8.8.4.4.
DHCP must have the same scope as the Routers (Default Gateways) scope (ie) 192.168.100.xx (xx being 2-254)

How do I log in to my NETGEAR cable modem?

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Router is 192.168.2.1. No problems doing admin on that at all. No problems with any connected devices, mix of DHCP and static ips.

Modem is 192.168.100.1 (written on modem)

I know the external ip address for my network since I use that for my router's OpenVPN
I just can't access the modem for admin from the internal side.

I already tried plugging the modem directly into my laptop and using the 192.168.100.1 and got the same error I am getting from a LAN connected PC.

But I'll go try run the ip/config directly connected to the modem.

 

Someone may have changed the Modem's IP address. When connected to computer directly, you can find the IP address in the IPconfig /all command.

 

That someone would have been me and I didn't change it. Below dialog is laptop connected directly to modem via ethernet cable. I don't see any address for the modem here, all I see is the ip address for the laptop I connected to it. As for DNS all I see is dead beef???

 

The Auto Config IP address of the modem is 169.254.136.41. Any IP address starting with 169.254.x.x means it does not have a Static IP address assigned to it. Or the ISP has not assigned and IP address via DHCP. I suggest Resetting the Modem to Default Factory settings and resetting it up with your ISP info again.

 

OK, I am officially confused. I have an external ip WAN address for the modem that is assigned by the isp and not static. I have no issues with that. I access my network remotely via VPN on my Linksys router all the time. My problem is the internal modem admin ip address that is supposed to be static and should be 192.168.100.1. How on earth can that not be the case unless the modem has been corrupted? Factory resetting it would probably involve a call to Comcast to get them to allow it back on their network. I hate to do that, but if I must... Or, maybe it's time for a new modem.

 

You most likely aren't using the correct IP address to access the modem's GUI, which is why it's probably timing out. See if you can find the modem's manual online and verify the address. I've never seen one where you can change a stand alone modem's IP address. The easier option is to contact Comcast. As long as your modem is online, they should be able to better check your signal levels and modem logs for errors or disconnects. The issue you're having sounds like it's on Comcast's side (from wiring to pole) if it's not a modem issue.

 

Yes, I am using the correct ip address. It's written on the modem and I have never changed it.

Yes, I agree, the problem I am having is exactly like last time when the outside cable went bad. I could see the issue from signal strengths in the modem GUI. But now I can't get to that GUI to check!

 

I don't know how your modem got corrupted except you said you tried to change the modems IP.
You shouldn't need to call Comcast once you reset the modem, just follow these instructions. How do I install and activate my NETGEAR voice cable modem? You may want to check with Comcast first to see if there is an issue with your lines or neighborhood.

 

Not sure where you saw that? ?? I never tried to change the modem ip address. I changed the ROUTER'S admin ip and DCP range because when you try to access servers an OpenVPN from another network with the same default admin (192.168.1.1) it loops back and fails. So I changed my ROUTER ip address to 192.168.2.1... and the devices on it to .2.xxxx. I just provided that info for background in case it had something to do with blocking the modem. Which it shouldn't.

I don't know how your modem got corrupted except you said you tried to change the modems IP.
You shouldn't need to call Comcast once you reset the modem, just follow these instructions. How do I install and activate my NETGEAR voice cable modem? You may want to check with Comcast first to see if there is an issue with your lines or neighborhood.

 

OK, don't overthink it or over-complicate the issue. Call Comcast. Your WAN IP has nothing to do with the issue, but if your modem has failed or is not letting you connect via DHCP, then you're not going to be able to connect to it's GUI page.

- And Yes, stand alone modems typically need to be provisioned from the ISP and don't have a reset button.

 

Exactly. They have the gear to test the cable and signal strengths. It is simple for me to do it ahead of time when I can admin my modem. But I can't.

.

 

Did you try the reset button on the modem? Press it for more than seven seconds until the lights blink and then see if you can connect.

 

No, I am afraid that if I do that I will lose connectivity until I deal with Comcast to re-provision it.

 

It's possible that Comcast has changed and/or locked your access to you can't get into the control panel. I have Verizon FiOS, so I can't really comment on Comcast practices.

 

No, it's not their gear, I own the modem. And the router. Not paying rental fees and providing open hotspots from my house.

 

As I said, call Comcast. If you see a reset button on your device, then it is Not a Modem, it's a gateway router that's in bridge mode. Resetting a gateway to factory defaults is going to put it back in router mode and enable DHCP.

 

Honestly I haven't looked. It is a Netgear CM 700 stand-alone modem. My router is a Linksys ACM 3200. I own both. No gateways here.

 

Sorry, I was wrong. I thought you were using Comcast equipment. Unplug power & the coax & ethernet cables from the Netgear Modem for about 5 minutes, then reconnect it with a computer connected directly to the modem with an ethernet cable. Run an IP config and see if you get an IP for your computer that's Not a 169.xxx address. Try accessing the GUI at http://192.168.100.1 again.

 

OK, guys, after all this checking ipconfig and hooking up the laptop to the modem several times and then back to the router, I decided to try to logon to it one more time from my upstairs ethernet PC via 192.168.100.1... and it worked. I don't understand. I have been trying this several times for the last week with several power cycles for all the gear with no luck. <scratching head>

I am just coming out of a battle with covid so the rest of the work on my network connectivity issue by looking at the signal strength and getting Comcast out will have to wait until tomorrow. I am sleepy. We'll see if I can get back into the modem then.

As for the covid, all I can say is I was glad I was fully vaxxed and boosted and it still sucked. But only for a week or so.

 

Glad to hear you are getting healthy and you probably sorted out your issue.

 

Thanks, man, although not really sorted. Tried to logon to the modem GUI this morning, same PC, same browser and it fails again.... can't reach page. I also checked my MalWareBytes settings and the GUI ip is in the allow list, so that's not it. I am going to have to give up on this for now, I suppose. Just don't know what is blocking me. Also fails on my MacBook that doesn't run MWB. Maybe I'll try to duplicate what I did yesterday by connecting the laptop to the modem ethernet and then back to the router. Not sure why that worked but maybe worth a try.

BTW, I took a brief look last night when I was able to access the modem GUI and the data looked good in terms of SNR and power. But I need to have that up and visible to refresh when I get the connectivity dropout. That's how I did it last time 10 years ago, anyway.

 

Start with a new Ethernet Cable. Meanwhile A quick call to Comcast 855-870-1311 or Chat will be able to test the lines on their end and narrow it down if it's their problem or yours. Being 10 year old or older modem, it may very well need to be replaced.

 

OK, I decided to humor you guys. I swapped the ethernet cable between the modem and router and guess what? I was able to logon to the modem GUI from my wifi laptop. But... just like last night when I connected the modem briefly to laptop directly to run ipconfig and then back to router... logging onto the GUI from a network PC worked only once. Now I can't logo to the modem GUI again from any PC. Same as in the beginning. Same as last night. The cable was not an issue.

So I am back to square one with my original question. Why can't I log onto this modem GUI? Whether or not I have an external coax input cable problem, which right now is secondary, I still have an internal issue logging onto the modem GUI. Either the modem is failing or the router is blocking it somehow.

This CM700 modem is only 5 years old. I installed it when I upgraded my service back then.

I have another router around. I am almost inclined to just get a new modem and change out both the modem and router and see where that takes me.

 

OK, I decided to humor you guys. I swapped the ethernet cable between the modem and router and guess what? I was able to logon to the modem GUI from my wifi laptop. But... just like last night when I connected the modem briefly to laptop directly to run ipconfig and then back to router... logging onto the GUI from a network PC worked only once. Now I can't logo to the modem GUI again from any PC. Same as in the beginning. Same as last night. The cable was not an issue.

So I am back to square one with my original question. Why can't I log onto this modem GUI? Whether or not I have an external coax input cable problem, which right now is secondary, I still have an internal issue logging onto the modem GUI. Either the modem is failing or the router is blocking it somehow.

I can't be of any help to you since you're all over the place and refuse to troubleshoot this logically and pragmatically.
Forget about the GUI! There's next to nothing you can change or need to do in there.
You're complaining about a disconnection issue - Connect ONE computer directly to the modem with a new ethernet cable and see if you still disconnect. Then you troubleshoot the disconnect issue by seeing if you have a valid IP address issued from the modem and pinging the modem for local connectivity. Everything else is a waste of time.

 

You can swap modems for test purposes. Swapping out the modem would confirm if it is the modem that is the problem or not.
But if you can login to the modem once, you should be able to make the changes that you need to do, then save the changes, and you shouldn't need to login again
If you need to login again, follow the troubleshooting steps you already tried. Unplug power to the modem, swap Ethernet cable, and plug the power into the modem again.

 

There are no user settings in one of these, IIRC. Just a bunch of MIMO channel biding info to create the bandwidth for the subscribed speed, power and SNR data. The "advanced" tab allows you to do a simple reboot or revert it to factory settings. The latter of which would require calling Comcast to re-provision it.


I suppose I could put another modem in there and just see if I can get to the GUI. It won't be functioning for broadband in that scenario.

You can swap modems for test purposes. Swapping out the modem would confirm if it is the modem that is the problem or not.
But if you can login to the modem once, you should be able to make the changes that you need to do, then save the changes, and you shouldn't need to login again
If you need to login again, follow the troubleshooting steps you already tried. Unplug power to the modem, swap Ethernet cable, and plug the power into the modem again.

 

Just a quick update: For whatever reason this morning I can easily log onto my CM700 modem. Still don't know what was blocking it before... and still don't know if this will continue. A snapshot of the modem data signals and powers look good. But... the event log shows that there are several T3 timeouts which I believe are my connectivity dropouts. So it is looking like an upstream cable problem.... or still possibly a modem problem, I suppose. The other challenge with that is that I own a piece of that. I have a coax cable running from my network closet out to where the Comcast service terminates under my deck. So, I will need to check that cable and clean those connections first. IIRC last time I had a similar issue I just ran a new coax cable though my door out to the service and ran for awhile like that to eliminate my main hidden cable as an issue. I just reset the cable modem log and we'll see what that does before I go further. here is an excerpt from the log:

 

Looks like you are on the right path to figuring it out. I am sure you are technically proficient in troubleshooting your Coax cable setup. But it might be worth a service call to have their technician test the line from the pole to your house, and your Coax line into your house just to be sure it's not the modem.

 

Yes, this is what I went through last time. It's either their cable or my cable. I have a hidden cable that butts to the Comcast service cable under my deck and then enters the house though the foundation, then up the wall, across the ceiling in a joist chase to the network closet. But I really screwed up when I installed that and did not run a spare. So, if that is bad, I am screwed... or in line for a couple days of work to open and then repair the drywall I will need to open in a few spots. Ugghh. Or I could connect back to the less secure cable that home runs on the exterior out back temporarily. But that is lower quality cable that came with the house for TV. Built in 1995.

I already cleaned, applied some dielectric grease and tightened the butt connection between the Comcast cable and my cable... but I have had another T3 timeout so that doesn't seem to have helped.

My next step is to run a fresh piece of RG6 coax directly from the Comcast cable to the modem through a window and run like that temporarily. Then check to see how the modem is doing. Hopefully that makes no difference which will mean it is the Comcast cable again. But you never know.

I also got onto the Netgear forum and some guy there who is more familiar with the GUI data beyond power and SNR is helping me interpret that.

But on a positive note, I have been easily able to get into the modem GUI all day. I still don't know what was causing that problem. Oh, well.

 

When I was living in upstate NY, I had similar random connection issues. After trying everything, finally did an end-to-end check of the cable...mice had chewed it up under the deck!

PS: nothing wrong with a spare modem/router. Good luck.