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This is about modifying my SMC-D3GNV which is a Cable Modem, a Wireless Router and a VOIP telephone adapter. While most people have their home networks configured nicely, when it comes to the cable modem Comcast often ships devices like this which unfortunately cannot be reconfigured easily if at all. Most people complain about very low quality of the wireless portion of this device which also applies for other makes like Technicolor, Cisco, etc. Unfortunately Comcast customized firmware has restricted the options that users can do to make changes to such devices by using the usual web interface. To be honest, some Comcast customers were able to make this device to work as a plain modem (Bridged Mode) thus disabling the Wi-Fi portion and the router just by calling Comcast customer service. Unfortunately that solution is not permanent and if you reset the device, you will be on Comcast CSR mercy again. Here in a few steps I will show you how to permanently disable the Wi-Fi section of this modem/router. This is reversible process and you may put everything back the way it was but I sincerely doubt that anyone would do that unless you must return the equipment back to Comcast.

Step 1: Disassembling the Comcast Gateway SMC-D3GNV

For this procedure you will need a Torque driver T9 for the screws removal shown on the picture. There are 4 screws on the bottom and 2 screws on the right side cover that need to be removed before you are going to pry the left cover.

Step 2: RF Module Removal

Once you remove the left cover you will locate the RF module in the upper right corner on the main board. You'll find three antenna cables with miniature connectors attached to the module. Remove the connectors and two screws that hold the module to the main board. Be aware that the screws have washers under the board and you must use needle-nose pliers to hold them under the board to be able to unscrew them. Once the screws and the cables are removed, remove the whole RF module. You may also remove the antennas attached to the cables, they are stuck with double-side sticky tape and easy to remove. Also you may leave the antennas the way they are since they don't have any function at this time. You may keep all the removed parts for later reassembly if needed.

Step 3: Reassembly of the Modem/Router

Put the covers back and screw down the screws without the RF module and use the device as a regular modem/router. The device won't even notice that you removed the RF module and it will report on its own web page that your Wi-Fi network is still active. This in case if you know how to log in (default address: 10.0.0.1, default username: "admin", default password: "password".). The main benefit is that there won't be any RF signal generated to already overused 2.4 GHz band. The signal that this device used to create was strong enough to interfere with other routers you may have especially that this type of device occupies 2 different channels at the same time overlapping 8 channels in the 2.4 GHz band hence using much more bandwidth than regular routers do. Mine was using both Ch.3 and Ch.7 which occupied almost the whole available band since one standard channel actually overlaps four channels (2+2 adjacent channels). It also used to create additional Xfinity Wi-Fi network to serve external unknown Comcast passing by customers unless you have disabled it. For this unauthorized bandwidth sharing for the Xfinity network, Comcast was sued by some customers.

Removal of the RF module also reduces the unnecessary heat dissipation and will keep the temperature of the device lower. For your Wi-Fi planning I strongly suggest you to use some spectrum analyzing software in order to choose free of interference channels instead of letting the device to do it for you. Comments and questions are welcome.

Step 4: ​Apendix: Network Configuration

This is about configuration of the LAN network following the modification on this device. You would usually connect a second or even a third Wi-Fi router to your LAN in order to get strong enough signal to cover your residence. You may connect all Wi-Fi routers in a daisy chain or to serve separate LAN networks. Look at the images to see which combination better works for you. You may still use all ports of all routers to provide Internet but the computers may or may not be on the same LAN with the rest of the computers (connected directly or wirelessly) depending on the combination you choose.

If you need all of your wireless devices to be on the same network due to media sharing, you need to use the daisy chain configuration. That means only one router may act as a DHCP server to assign IP addresses to all network users (doesn't matter which one) while the other router(s) must have DHCP server disabled. Also the home IP address of the routers themselves should be in the same subnet , e.g. 192.168.0.1 for the first router, 192.168.0.2 for the second, 192.168.0.3 for the third router etc. In this case you will not use the WAN port on any router since the second and the third router (if needed) actually will not be routing anything, they will act as access points in this case. The inter connection will be on the LAN side only in order to preserve the same subnet.

The other combination is when you don't care about sharing files and other media among the users so you will leave the routers to do the routing and each one's DHCP server will have their users assigned IP addresses in their different subnets with IP addresses as shown on the pictures. In this case the WAN ports are used normally as an Internet connection from the previous source, whether it is the main router or the second router's LAN port.

Step 5:

<p>I have an Arris TG1682G. Does this same process work for this device?</p>
I honestly don't know the hardware configuration of that model. I guess it should be similar with a Wi-Fi module. You might have hard time opening the case since every manufacturer has a different design. Be careful not to brake the plastic covers while doing that.
<p>Thanks for the feedback. On the outside the two units are virtually identical. I'm a little nervous about causing irreparable damage by opening it though. My goal is to turn off the wifi do to health reasons in the household. Any other suggestions?</p>
<p>excellent tutorial! i have been trying to close my exploitable holes in the network and this constitutes a huge glaring hole! i already have had to disassemble several pc laptops and am using a macair which suddenly had a new user which upon looking at his added script collects my credit card info as well as other info that is too gruesome and disturbing to see. all my machines are going to be linux with a very secure subsystem in place!! thank you again!</p>
<p>I am sorry to hear about your situation. It must be horrible to be a victim of identity theft. You can never be sure when it is going to hit your door. Take care.</p>
thank you so much! my brother is an attorney and told me about comcast,xfinity being sued for just these problems. i thank you kindly for the idea to do just what i should have a while ago. i am happy to help out others, but not at the expense of our information! this is a great start ! thank you again!
Can't I just desolder the crappy antennas and run 3 new rg316 coax to a dipole 9dbi antenna for 2.4, a clover leaf 5.8, a a patch antenna? Or wire it to my own diversity controller? They are cheap to make! I make antennas and transmitters and receivers in 2.4 and 5.8 for my RC models all the time! Adding the higher gain or directional antenna with existing dbm would theoretically give me better reception and range!?!
Yes, you can absolutely use alternative antennas with high gain and narrow angle direction but don't forget that adding RF coax cable will introduce signal loss which is significant on this high frequency (2.4 GHz) if you don't have a special RF cable.<br>The only way to compensate the cable loss is to insert an LNA after the receivers antenna and a PA before the transmitters antenna. Honestly I don't know which one is which and what is the third antenna doing in there. If no amplifiers are added then it's easier to detect which one is the right antenna. Just be aware of those crappy connectors used to connect on the wireless module, they are not meant to be toggled several times. I used to make antennas my self long time ago (when I was HAM Radio) but it's nice area to experiment since it's the easiest way to gain the signal without complications of the electronic circuitry. The installed J antennas are not so bad, the problem with any antenna is if it is hidden in the box where the signal level is very low. Putting out an antenna in order to reach longer distance is the best way but the risk of the above mentioned cable loss is still there. Good luck with your project.
<p>The blog was a good effort for Comcast password recovery . However finally I have to take help from 25dollarsupport.com to resolve my problem . Thanks , it is fixed now. Prompt and well behaved.</p>
<p>I highly suggest going and buying your own Docsis 3.0 modem. Being that I work for ComCast as Wireless Technical Support, I deal with this modems day in and day out, and I have to say they are horrible to begin with. Not only is the custom firmware crap, but the hardware alone is junk. That does not just for the SMC, my opinion is for all of the Wireless Gateways they use. Arris, Cisco, Technicolor, and SMC.</p>
<p>You are correct in general. How ever the things are not the best even with standalone DOCSIS 3 modems. I bought from Best Buy a Motorola SB6120 for $100 about two years ago. While it was serving fine at the beginning, it gave me lately several hiccups before it died completely. Not to even mention that Xfinity tech that came to establish the cable connection for the first time said that it was a terrible choice to buy such modems. Thus he couldn't even make it operational and left the job unfinished. I was able to do it myself the same evening after reading some tips online (Thanks God for the Internet). </p><p>While this SMC Gateway fails miserably as a Wireless Access Point due to very low quality RF module and Xfinity Network addition occupying 8 channels in total, it has pretty good hardware for 1 Gigabit router. I can't find any issues regarding the routing ant serving the LAN except the crippled and limited options firmware. I just wish there was an Open Source firmware for it to unleash all the options as it was done with Linksys routers. </p>
You are going into Comcast's property and that in and of itself is a violation of the agreement you signed with Comcast and makes you liable for it and problems the equipment has after that. Comcast WILL come after you for the cost of that device if something goes wrong and the device no longer functions properly. Take it from a Comcast employee that has had to do this to a customer renting the gateway from the company.
<p>Well, you got me here. As for the customers who are afraid from Comcast and don't want to deal with such devices with crippled firmware I suggest you to switch to another internet service provider. That way you won't have to deal with such problems because their modems are fully configurable so you will not see problems like this. This was an innocent reversible modification but as you said it, do it on your own risk. Period.</p>
If you do this and it doesn't work, you just bought that device from Comcast. It's not cheap either. Do this at your own risk.
<p>Why it wouldn't work? I am not writing theories here, I just did it and it works beautifully. I got rid of this router's RF signal which was polluting 8 channels on the 2.4 GHz band yet not providing good enough signal for my residence. As far as the Comcast deal, you usually don't buy this type of equipment from Comcast, you only lease it. In case you need to return it back, you just put back the way it was and you are done. Just don't remove the antennas from their spots so you won't have to remember where they were installed. Some of these are on sale on Craigslist or on eBay but those are not really sold by Comcast, they are just not returned equipment.</p>
<p>So, you still connect your own wifi router to this Comcast box by Ethernet cable, right?</p>
<p>The device will continue to work as a modem/router without the Wi-Fi section and you may connect you second router on any port of this router. I will try to update my instructable with a configuration tips for two routers combination.</p>
<p>P.S. I ask because that's how my home wifi network is hooked up now to the &quot;old&quot; Comcast cable box (my router into their box via Ethernet cable). They're nagging me to &quot;upgrade&quot;, which I've been resisting simply because I don't need the hassle of driving 20 miles to get the &quot;new&quot; box, hooking it all up, etc. Pretty soon they'll probably force the issue, though,.</p>

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