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I have a Motorola NVG510 modem from AT&T, and I would like to disable all routing functions and use it as just a modem. I have a Time Capsule that's already connected and broadcasting its own wireless network, which is how I've been connecting (it's been reporting a double-NAT error, which I assume is from the NVG510 also acting as a router).

I followed the instructions in question six here, and I can connect as I did before, but my Time Capsule still has a double-NAT error.

How do I put the NVG510 into bridge mode or otherwise fix the double-NAT error? (No, ignoring it does not count as a fix.)

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Is it possible to use the device only for wi-fi needs? I switched to comcast and have a motorola cable modem, can I connect it with nvg510 for getting a wi-fi signal? –  Harpreet May 16 '13 at 0:21
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3 Answers

up vote 1 down vote accepted

I use to have this very modem and I think I speak for everyone when I say this thing sucks! However, there is hope. It sucks bad enough that I decided to crack it open and do some soldering onto it to get to a root shell. From there, I discovered a root escalation vulnerability in their web user interface.

What all this means? You can root your modem with a specially crafted HTML page, and configure it into a "true" bridge mode. In this bridge mode, literally the ptm internet interface is short-cut through to an ethernet port, rather than going through the NVG510's router. This means the NVG510 can't even connect to the internet and will forward everything to one of the ethernet ports(which then goes to your router).. So, for instance, when you make a DHCP request for an IP, you get a response from AT&T's servers, not the NVG510.

I wrote a blog post explaining how to root it, and then enable true bridge mode on my website.

However, I must warn you. It's dangerous to do this and could possibly brick your modem. It's fairly difficult to brick the modem, but it's still a possibility. Also, it requires some experience using advanced things like telnet and familiarity with a command line.

Also, if my blog post is a bit too technical for you, or you don't have time to deal with it, I've made a $1 Android application called NVG510 Fixer. It fixes the most common problems (including bridge mode) just by the push of a button. No knowledge of telnet or HTML required.

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I would definitely do this, save for the possibility of being banned from their networks…though that might not actually be a bad thing, considering all the trouble I've had with them! –  Blacklight Shining Apr 27 '13 at 17:18
    
@BlacklightShining I can't make any guarantees, but I had my modem bridged for like 9 months without anyone saying anything AND I've seen actual AT&T employees reference my work before for how customers can fix their own problems –  Earlz Apr 27 '13 at 23:46
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From what I can tell, by digging around online a little, the NVG510 is not bridgeable.

There is a "workaround" on AT&T's forums, which may help. Honestly though, I would just research a cheap modem (not a modem/router) that would do what you want and go out and buy that.

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Yeah, this thing has been really frustrating me. I really should just buy a modem myself. –  Blacklight Shining Nov 1 '12 at 22:36
    
I have never been happy with the modems supplied by ISPs. Given the price of them I find it easier to just buy the right one for my needs. –  Windos Nov 1 '12 at 22:42
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Is it sufficient for your purposes to put the time capsule in bridge mode? That will fix the double NAT error. At least you get the TimeCapsule's wireless capabilities, though you get dhcp from the Motorola still...

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I'd really rather not…I like my 10.0.1.1/24 subnet and my .local search domain. Also, the Motorola modem has an unremovable .att.net search domain IIRC, which is wrong on so many levels. :I –  Blacklight Shining Apr 27 '13 at 17:07
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