Cannot reach modem configuration page through router

tacomaguy20 · Sep 29, 2018

I recently purchased a Motorola MB8600 modem to go along with my TP-link WDR3600. I cannot reach the modem configuration page when the router is connected (the page times out). However, the internet works fine and I can reach the configuration page when the router is bypassed. The default IP of the modem is 192.168.100.1 and the default IP of the router is 192.168.0.1. I did not have a problem getting to my old cable modem's configuration page when the router was connected. I am guessing either Motorola has some restriction on this for security or I have my router settings wrong. Everything is hardwired. Any help would be appreciated.

jsmithepa · Sep 29, 2018

ISP --> R1 --> R2.

Both your R1 and R2 are NATing (converting one IP range to other).

Solution, reconfigure R2 for Access Point (no NAT), then the prob will disappear.

tacomaguy20 · Sep 29, 2018

Not sure exactly what that means but I do see an option for NAT on my router. It says current Nat Status: Enabled. Current Hardware Nat Status: Enabled. Should I disable them both?

*Update* I tried disabling both and lost internet. I tried disabling just hardware and didn't help. Enabled hardware and turned off the other and no internet again. Maybe I misunderstood. A little more explanation please.

tacomaguy20 · Sep 29, 2018

Ok found the sticky on how to configure my router as an access point. I can now access my modem settings but now my router cannot be accessed through the new IP address I configured. Also, I have wireless devices that I need to access from time to time through their configuration pages as well. Like my Stereo receiver and wireless printer. Since I've disabled DHCP on my router, how do I find those devices?

bill001g · Sep 29, 2018

You only have 1 router and 1 nat so you need to leave it on.

I have always been somewhat surprised this worked since the modem is somehow intercepting that IP address even though it is technically in the wrong subnet on the WAN port.

I was also surprised consumer router send private ip address out the wan port. I know on commercial routers you intentionally prevent private ip from being sent to the internet.

It almost has to be the router some how limiting it. Maybe a firmware bug ?. I have used that exact modem at another house behind a asus router and you can access it just fine.

tacomaguy20 · Sep 29, 2018

I tried changing the IP address of the router to 192.168.100.253 to see if that helped but it did not.... at least not until I followed the steps in the sticky to change the router to an access point but now I can't access the routers configuration page so I've effectively just swapped one problem for another.

bill001g · Sep 29, 2018

You must have a router someplace. If the modem was a modem/router combo then you could use a AP. Your problems are actually much worse than not being able to access the router when it is set as a AP. Your modem only provides a single IP address so only 1 devices will work.

That is the main purpose of a consumer router is to share that 1 IP address with all the devices in your house.

tacomaguy20 · Sep 29, 2018

bill001g :

I do I have a router connected to my modem. That's what I said earlier. There is no chance that I have a second router. You say my problems are much worse. Please explain.

bill001g · Sep 29, 2018

Maybe things are unclear.

You only have 2 devices the modem and the router ?

If you converted the router to a AP then you do not have any router you made it into a AP. You have to have the NAT function that a router provides.

tacomaguy20 · Sep 29, 2018

Yes only 2 devices. I converted the router to an AP thinking that would help at jsmithepa's suggestion. It caused another problem so it didn't work. I reverted back to what I had in the beginning. Nat settings are both on and my router IP and DHCP settings are back to what they were when I started. However, I think I might have stumbled onto another symptom which may be causing this. I cannot reach any IP addresses outside of my private network. I can reach my other computer, my wireless printer, my wireless receiver, and my router configuration page all through the IP address. However, I cannot reach my modem or any other website through the IP address, only by typing the www address in the browser. I however can ping these IP addresses just fine. So for some reason my browsers (all 3 of them) will not go to the IP address of websites. They all time out. It's the same on my other computer.

bill001g · Sep 29, 2018

Well dirty way to fix that is put 192.168.100.1 in the host file and map it some made up url name.

It does not make a lot of sense since technically you always access sites via the IP address. The machine does a DNS lookup for the site and then opens a session with the IP address.

Many web sites are dependent on the URL since it is embedded as part of the HTTP stream.

Does the modem respond to a ping command.

tacomaguy20 · Sep 29, 2018

Yes is does access the modem through ping, just not by typing in the IP address in the browser. I don't know how to configure the host file but I'm thinking I have a bigger issue. Why wouldn't the ip addresses of google. 8.8.8.8 and 8.8.4.4 open but I can go to www.google.com just fine. Could it be possible there is an issue with the modem or router not finding the IP but only the alphabetic name somehow?

jsmithepa · Sep 29, 2018

One more time.

Leave R1 as is.
Configure R2 as AP, can assign an static for it for management, DHCP OFF here.
R1 DHCP then should be configure, say .1 to .31 for statics, and .32 to .255 for DHCP pool.

The idea is, you end up with a single subnet, where everybody can access everybody.

bill001g · Sep 29, 2018

8.8.8.8 is a DNS server not a web server.

I would suspect the web browser is the issue. Maybe firewall rules in the pc ?

You may have to enable telnet in wondows but a way to test ports is to do

telnet 192.168.100.1 80

If you hit enter or maybe type /GET you should see something. It is purely to see if traffic goes through. It will look different than using a different port. This is hard to describe.

You could load wireshark. Then you would actually see the data. You should see a SYN packet sent to 192.168.100.1 and a response come back as syn-ack. Your machine will then send a ACK and the session should be open. It should perform like this both with the web browser or if you use the telnet.

tacomaguy20 · Sep 29, 2018

jsmithepa :

Earlier I tried to configure my router. (R2 I guess) as an AP per the sticky in the wireless forum. I turned off my DHCP and I connected the modem to one of the non WAN ports. I could access the modem but then not the router configuration page. If you say I can assign a static address for it (the router). Please let me know how to do that because I changed the IP under the Lan settings and I couldn't get back into it and had to reset the router to default.

tacomaguy20 · Sep 29, 2018

bill001g :

Oh your right about the DNS server. Turns out I can get to microsoft.com through the IP address so that seems to work. I tried typing telnet 192.168.100.1 80 and it says could not open connection to the host on port 80. But pinging it works fine. I also disabled my firewall to test and no luck

tacomaguy20 · Sep 29, 2018

Finally figured it out. Turns out that I needed to change my Router ip from 192.168.0.1 to 192.168.1.1. I left the Modem 192.168.100.1 and subnet mask 255.255.255.0. were fine. I didn't have to change them and I didn't have to change my router to an access point either. DHCP is on and working. What I figured out was that I had to assign my computer to a DHCP reservation and then go to the IP & MAC binding settings and bind the MAC address of my computer to that same reserved IP address by enabling the ARP binding. Anyways after the binding was on it took me right to the modems configuration page. I can now access the modems configuration page and the routers configuration page. Hope this helps someone else as it was a pain to figure out.

tacomaguy20 · Sep 29, 2018

Further update is that I'm not sure the ARP binding is required. I think the IP address of the computer I am accessing the modem from just needs to have a DHCP reservation. More testing is needed but it works for now.

bill001g · Sep 30, 2018

That is a very strange restriction. The default IP the router uses don't work but you change them to others and they do. Sounds like a bug but after a quick search of that ip you find other posts from years ago saying that trick works so they have no interest in fixing it.

jsmithepa · Sep 30, 2018

Once you change any subnet, you must reboot everything. Cannot assume, change one piece, and the rest of the LAN falls into place.

Cannot reach modem configuration page through router

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