TUTORIAL: How to use your Personal Cellspot behind a Comcast Business Router

  • 28 September 2014
  • 10 replies
  • 396 views

I spent a bit of time struggling with this last week when my Cellspot arrived, and figured I would pass this short tutorial on to the community in case they need it.

 

If you have Comcast Business Internet services (rather than the cheaper but less flexible XFINITY service) you know that rather than providing a simple cable modem they give you a 4-port gigabit router. This router, while serviceable for basic use, lacks most of the features found in the Cellspot. Additionally, if you put your Cellspot behind the Comcast router, you will run into issues with NAT on systems that go through both.

 

To remedy this, you can either buy your own cable modem from a very small list that are supported by Comcast for use on their business service, or you can do the following:

 

1. Log into your Comcast router by accessing it on your LAN through a wired connection. The default IP address is 10.1.10.1, and the default username and passwords are cusadmin and highspeed.

2. Go to the LAN menu (on the left side menu), and uncheck the box for Enable LAN DHCP. Hit the Apply button.

3. Go to the Firewall menu (again, on the left side menu). Under the DMZ tab on the Firewall menu check the Enable DMZ Host, and then put an appropriate address in the box. 10.1.10.2 is a good choice. Hit the Apply button, and log out of your Comcast router.

4. Connect your Personal Cellspot to one of the ports on the back of the Comcast router, and log into your Personal Cellspot router via the instructions given with it. It's best to use a wired connection here as well if possible.

5. On the Cellspot router management interface, go the the WAN menu (from the left side menu).

6. On the Internet Connection tab, set the WAN Connection Type to Static IP, and then under the WAN IP Setting section put in the IP Address you used in step 3. For Subnet Mask use 255.255.255.0, and for the Default Gateway use 10.1.10.1. Hit the Apply button and wait for the setting to apply.

7. Move any devices you have connected to the Comcast router's ports to the ports on the back of the Personal Cellspot (except the Cellspot itself, of course). You may need to reboot all of the devices connected to your LAN or WLAN to get them to work right.

 

With this completed, your Comcast router essentially becomes a modem and you may now use the substantially more powerful LAN features of your Cellspot router instead.

 

Any questions, feel free to ask.


10 replies

Jim:

I have a Cisco DCP3939 2 band Wifi Gateway which is probably very similar to yours. My interface address is 10.0.0.1. I also just received a cellspot router as well. Do you think you could give me a hand to set up my router to work with my Comcast consumer gateway?

Thanks

corgi111

What happens if you now try to activate DDNS and/or VPN server on the TM-AC1900?

The process should be similar. Disable the DHCP server on the router, find the DMZ setting on it and put in an IP that's in the same subnet as the router's internal range (10.0.0.x, where x can be anything from 2 through 254), then set the Cellspot to that address as above. You may also want to disable any firewall on the Cisco side if it is turned on by default; on my SMC it was turned off so I didn't need to.


drnewcomb2 wrote:



What happens if you now try to activate DDNS and/or VPN server on the TM-AC1900?


The DDNS works fine - I'm using that myself - but I can't speak to the VPN as I use a different solution. It should work fine, though; by putting the Cellspot in as the DMZ, all packets should be forwarded through to it. There are some apps that are sensitive to the double NAT you get by doing it this way, but I haven't seen many, and most work fine despite them throwing a warning, like the network check on my Xbox 360.

The reason I asked is that connected to my UVerse gateway it would not run the DDNS client if there was a private IP on the WAN. I had to put the TM-AC1900 into DMZ+ and use DHCP. This assigned the router the WAN address of the UVerse gateway. Until I did that, it would not run the DDNS client or the VPN server.


drnewcomb2 wrote:



The reason I asked is that connected to my UVerse gateway it would not run the DDNS client if there was a private IP on the WAN. I had to put the TM-AC1900 into DMZ+ and use DHCP. This assigned the router the WAN address of the UVerse gateway. Until I did that, it would not run the DDNS client or the VPN server.


That's essentially what my instructions do; it sounds like you have to do something slightly different with the DHCP than we do, but the results are the same.

You actually CAN leave DHCP on on the Comcast one, but I found that the setting tended to reset itself when the you set the lease time to infinite (probably when Comcast pushes a firmware change), which would change the Cellspot IP and mess everything up. By disabling DHCP and manually assigning an address that problem went away.

Thanks for the reply I am not sure I can turn off the DCHP but if I can't I will post again. Thank You Very Much.

corgi111

This is some really great info, jturnley,

I'm moving it into the Wi-Fi CellSpot Router space. 😊

I can't turn off the DHCP on my Comcast supplied consumer Gateway. It is wireless N 900 2 band 2.4 and 5 GHZ. Tmo suggested since my gateway is working fine for my wireless network at home that the easiest thing I could do was to leave my network alone and plug the cellspot router into one of the 4 gateway outputs and use the cellspot for my cellphones only and keep using the Comcast Cisco DCP3939 for the rest of my home network.I am satisfied with my Gateway and my home network is working just fine. If I do this without putting my gateway into bridge mode will I get a double nat on my cellspot for my phones and does this matter. What setup would you use. I don't want to call in and put my gateway into bridge mode. If I just plug the router into the gateway I have one wired computer on my network, do I plug it into the cellspot or do I leave it plugged into the gateway. I would like to see both interfaces at the wired computer if I can.

Thank You

corgi111

Exchanged wireless gateway for eMTA problem solved.

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