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Obviously, when I connect cable modem directly to laptop using LAN cable I can access it (http://192.168.100.1).
But when router is between my laptop and cable modem it's obviously not as easy as that... what I am wondering if there is a general approach on how to solve this? Forward some port on my router so that when I http://192.168.1.1:8080 from laptop goes to http://192.168.100.1:80 on my cable modem? How would I configure that on my router?
Router: Asus N66U router with custom Merlin firmware
Cable modem: Motorola SB 6141
nikib3ro
Posted 2016-02-02T00:39:25.223
Reputation: 212
It seems to me that he's misstating it. Routers must be behind modems, there's no other way to do it. Unless your router has a coax or phone connection, in which case you wouldn't need the modem. Additionally, OP states "But when router is between my laptop and cable modem" – MagnaVis – 2016-02-02T03:59:16.793
Precisely my thought. In that case, the OP will need to verify that their modem supports remote management and if enable it. As discussed here (http://superuser.com/questions/872062/how-to-access-my-adsl-modem-configuration-remotely-over-the-internet) that is not always support for practical security issues.
– user5870571 – 2016-02-02T04:02:10.567True, though OP did also say that he can get to the management page when plugged in directly to the modem, so I have to imagine that it's enabled (and usually is, especially on the Surfboard line). – MagnaVis – 2016-02-02T04:03:33.317
1But that would only indicate that LAN management of the modem is enabled not remote management. – user5870571 – 2016-02-02T04:05:16.967
1OP is trying to manage it over the LAN. OP hooks up a router, then connects internally to the router. Then cannot get to the mgmt page of the CM. OP is not trying to access the CM's mgmt page from outside the network. – MagnaVis – 2016-02-02T04:07:35.813
1I misunderstood what the OP was asking then, because I couldn't figure out how the modem would be behind the router and providing network connectivity to the WAN port of the router at the same time.
I think what the OP meant to say then was "How to access cable modem dashboard from computer, when the computer is behind router?" I have updated my answer to reflect that. – user5870571 – 2016-02-02T04:15:55.583
1Your update more clearly reflects the problem, but it's not actually the case that the modem cannot be accessed once a router is hooked up. In fact, I've tested with several devices tonight and all of them still work on the private address of the modem (192.168.100.1). The only difference is what device has the public IP, even when the computer is hooked up to the modem directly and gets the public IP, it can assess the local address of the modem. The same happens when a router is hooked up. – MagnaVis – 2016-02-02T05:27:01.213
1Right but if the router WAN gets the public IP, then the the request from a computer connected to the router LAN has no way to be routed from private IP 1 (router LAN port) to public IP 1 (router WAN port) to private IP 2 (modem LAN port). Do you see what I mean? – user5870571 – 2016-02-02T05:31:14.180
1I see what you think you mean, but it's just not correct. I'm in the exact environment you described, and it works for me to navigate to 192.168.100.1 from my computer (which is 192.168.9.25). Because of the fact that 192.168.100.1 is such a commonly used address for a CM or similar device, every single SOHO or personal router I've tested supports this. I've tested on 2 different higher end (one enterprise, and one carrier class device) and it it also works on both of those. I'm running a Ubiquiti ERL at home, and it works as well. – MagnaVis – 2016-02-02T05:40:07.653
1I tried it on an Arris modem and indeed you are correct. It works for me too. I can only then suspect it is a modem specific issue. – user5870571 – 2016-02-02T05:41:23.907
1That's possible, but I do doubt that as well (just given what I know). Because 192.168.100.1 is a non-routable IP address, one would figure the router would have to know to try it out of the WAN port anyway. Generally speaking, I would figure that other non-routable ranges are dropped if there's no route available for them defined in the routing table of the router. Now, I don't know that for sure, but I can test it tomorrow to see if that's the case. The test is simple enough, statically assign a device 192.168.30.1 as it's address, hook it up to a switch outside the router (cont) – MagnaVis – 2016-02-02T05:47:08.077
1and also hook the modem into the switch. The router will get the public IP like always, then I can try and connect to 192.168.30.1 from inside my network and see what happens. I'll report back, because this is an interesting question about routing design for SOHO routers. It actually wouldn't surprised me if it worked, just as a mechanism for dealing with stuff like this. – MagnaVis – 2016-02-02T05:48:49.423
1Please do, I would be very interested to see what your results are. – user5870571 – 2016-02-02T05:53:12.013
1Well, the routing table for my ERL shows 0.0.0.0/0 to be routed out of the WAN port as the default. This includes non-routable ranges, so I imagine that any device on a "private" IP (10. or 192.168) would also go out of the WAN port. But, the next hop address is my ISP's router, so I don't know by what mechanism a device would step in between that. I suppose it's possible that the ISP's routers have rules on them to send non-routable traffic back down to the client... I'll let you know what I find. – MagnaVis – 2016-02-02T05:55:55.723
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This diagram http://www.dslreports.com/forum/r20674896- discusses exactly what we are and why it works (either a static route or routing protocols). I just didn't think of traffic from a WAN port with a public address being routed to a private address on an upstream device. That is really interesting.
– user5870571 – 2016-02-02T06:00:03.330@user5870571 It seems title caused confusion - I wanted to describe situation in which there is outlet -> modem -> router -> laptop... so modem is "behind" router from "laptops perspective". I've updated the title to prevent further confusion. And, I've figured out the problem... see my updated answer: http://superuser.com/a/1034417/72793 . I'll upvote you guys anyway since your discussion helped me solve the problem.
– nikib3ro – 2016-02-02T15:57:24.200