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Comcast Xfinity Firewall and Microcell

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Comcast Xfinity Firewall and Microcell

This is a warning - if you have Comcast Xfinity internet, make sure the modem/router's firewall is set to Medium/Typical security.  If it's set to High/Maximum security, the Microcell will not successfully connect to the AT&T servers.

 

Details - our street lost DSL service due to a building fire destroying the 50-pair aerial cable.  As a temporary workaround, I got Comcast Xfinity internet added to my cable TV, using their modem/router model DPC3941T.  During the Comcast Xfinity setup, I chose High/Maximum firewall security.  The Microcell (white DPH-153) would not connect to AT&T.  (The Microcell got solid green power and internet lights, blinking green GPS light, and red 3G light.)    I checked Otto Pylot's excellent technical reference, which indicates which ports need to be open on the firewall.  Even though the Comcast Xfinity documentation indicates that the High/Maximum security setting has the proper ports open, I changed to Medium/Typical security and the Microcell successfully connected.  

 

Thanks again to Otto Pylot for all the contributions he makes here.

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ACE - Expert
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Accepted by StillDSL
‎07-03-2019 4:16 PM

Re: Comcast Xfinity Firewall and Microcell

@StillDSL - Thank you. It's good to hear that my Tech Guide is still usable. The flashing green GPS light just means that the MicroCell is performing a location check. It should turn solid green when done, but that doesn't mean that location was verified. If the 3G light is red, that usually means the location verification failed. You shouldn't use firewalls with the MicroCell unless you set provisions in that firewall to port forward the required ports to the MicroCell.

 

You might want to consider switching to WiFI-C (WiFi Calling). The MicroCell reached its EOL at the end of 2017 so AT&T doesn't sell them anymore. Service will continue until AT&T begins to transition away from their 3G network. We highly recommend that you switch to WiFi-C. There is no ETA on when the transition will begin, so.......

___________________________________________________________

MicroCell Technical Guide by OttoPylot

Cellular Booster Guide by OttoPylot

"Quick Tips: My Microcell Doesn't Work"


I am not an AT&T employee.

Award for Community Excellence 2019 Achiever*
*The views and opinions expressed on this forum are purely my own. Any product claim, statistic, quote, or other representation about a product or service should be verified with the manufacturer, provider, or party.
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Tutor

Re: Comcast Xfinity Firewall and Microcell

Hi @OttoPylot ,

 

Unfortunately the Comcast Xfinity modem/router is a combined device, there's no way to use the alternate connection method of putting the Microcell between the modem and router so that it's outside the firewall.  It has a dumbed-down interface, so it's not easy to figure out how to do individual port forwarding on this device, since its documentation already claims the ports needed by the Microcell are already open.  I'm just glad the Medium/Default setting worked, since I'm not running my home network without at least that level of a border firewall.  As soon as the 50-pair cable is replaced, I'm returning the Comcast Xfinity device and going back to my DSL setup where I have much more control.

 

My AT&T-branded Galaxy S4 does not support WiFi calling.  (T-Mobile-branded Galaxy S4s do support Wifi calling, but at the time S4s came out, I guess AT&T considered Microcells to be a better solution than WiFi.)   I realize that AT&T plans to drop their 3G network entirely, but right now my street can only receive 3G signals, even though AT&T's coverage map says my street is in the middle of a 4G LTE area.  I do get 4G LTE elsewhere in town, so whenever AT&T gets all of the 3G towers upgraded to 4G LTE and/or 5G, I guess I'll need to buy a new phone.

 

Message 3 of 4
ACE - Expert

Re: Comcast Xfinity Firewall and Microcell

@StillDSL - yep. Gateways are problematic. When I had DSL, I just used the supplied modem, set it to bridge mode, and used my own router. Now that we have Comcrap, I still use my own equipment (modem and router). I have setup the MicroCell here a couple of times to do various tests for folks and never had an issue connecting thru Comcrap.

 

AT&T will only support WiFi-C on most of the phones they sell, but if you have one branded from another service, you're s.o.l. as far as WiFi-C goes.

___________________________________________________________

MicroCell Technical Guide by OttoPylot

Cellular Booster Guide by OttoPylot

"Quick Tips: My Microcell Doesn't Work"


I am not an AT&T employee.

Award for Community Excellence 2019 Achiever*
*The views and opinions expressed on this forum are purely my own. Any product claim, statistic, quote, or other representation about a product or service should be verified with the manufacturer, provider, or party.
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