Hi Peter,
Thanks for getting back to me (us), and thanks to Trouble for pitching in here with the information.
As Trouble mentioned, yes you
DO have RJ45 ports on your Comcast cable-modem box in your pics (thanks for posting those back by the way; that's a tremendous help!). There appear to be 4 of them. The thick yellow cable with RJ45 and the thick grey cables are plugged into those ports in the middle of the Comcast box.
Here's a link to a wikipedia article on RJ45 & Ethernet which more fully explains the connectors (physical media) and the Ethernet standard:
https://en.wikipedia.org/wiki/Ethernet There are also photos of Ethernet cables. These are the same ones you can buy at Radio Shack, Staples, Walmart, and yes even Home Depot & Lowes and most Ace hardware stores. In other words they are readily available everywhere.
The photos you have clearly show the main Comcast Cable-modem box, and the eMTA box, but the eMTA box it's hard to see the entire box; it's probably what you are referring to as the Gateway. This is comparable to the 2nd box that Charter and Cox use for digital phone or TV connections here in SoCal. I have a good friend who also lives in SoCal who has been on Comcast for years, and
does not have this setup you have (she's about 100 miles from me). I'm guessing this is an East-Coast or possible Midwest implementation that Comcast is using (a la Charter & Cox) when you add a digital phone or digital TV service to your Internet. Your profile says you live in Maryland, so it's something they do back there, but not here on the West Coast.
Since it sounds like you have things working, thanks to Trouble and I, you're probably good to go if you Galaxy wifi speed is ok, you may be running on the wifi part of the Comcast box, and that's fine.
You can also connect the Belkin wifi router (so you do have wifi on that device!!), to your Comcast box as shown in my diagram on my previous post, and also use your Belkin wifi router to connect your wireless devices such as laptops, tables, or smartphones to your Comcast Internet. The Bridging setting Trouble mentions helps to define 2
"sub-networks" and link them together via the Gateway box to prevent IP address conflicts and routing issues between the 2 wireless networks you are creating when you plug the external Belkin wifi router into your Comcast Cable-modem box.
In my neck of the woods, SoCal, major ISPs
do not require your 2 wireless networks to be bridged as in Trouble's case. I have both business and home Customers running 2 wifi networks together simultaneously on both Charter & Verizon without necessitating the Bridging function.
This is probably due to the internal differences on how Comcast routes their ethernet traffic and the configuration of their servers and networks. Comcast is also using a device that cannot separate 2 subnets, and therefore the DHCP and the duplicate IP addresses (along with NAT) are handled properly by using the Briding function in the Gateway box (my guess). This is a crude workaround, and eventually I suspect they will replace the Cable-modem box you have with a smarter one such as the Actiontec's that Verizon is using or the Motorola Surfboard's that Charter is using here. The boxes Comcast are using aren't dumb exactly, but when it comes to wireless subnetting, they appear to be mildly-retarded compared to smarter hardare being used out here on the West Coast! LOL.
In fact, on my personal home network I can flip between the DSL modem internal wifi and my Cisco/Linksys external device wifi at will on multiple devices without the need for Bridging between the 2 different subnets. This works on Verizon as I said, as well as on Charter, and Cox. These "smart-modems" now can do subnetting and NAT automatically.
Hope this little discussion proves helpful and provides you with some good information. In the old days, I use to help build ISPs and sell them equipment to get started.
Best,
<<<BBJ>>>