As I understand, most cable companies do not support multiple connections to the modem and if they did, they would charge extra fees for the additional IP address. I have a MB6800 modem which does have multiple RJ45 plugs, but Comcast does not support them at least in my area. The most common setup is connect the modem to the router and use the ethernet ports on the router for your PCs.

in general. im not sure its the situation on my end. my cable company supports told me that if i will enable bridge mode on the modem, i will be able to connect only to the first ethernet port.  

they see from their end that the bridge mode is disabled, but on my modem UI, in the option:  Activate Bridge Mode, i can see V selection near it. so i guess it is working, and anyway on same time, my both pc's can run the internet. so im not sure they really blocking some of the ports. 

 

the modem is in one place, and for 20 years, i have rj45 cables from the rooms to the modem area, inside the walls, i cant change it. and the routher i just put on some path way of the house. i cant connect the pc's to the router in pretty way. 

Can you move the router next to the modem and still get the WIFI coverage you need? If not maybe an extender or mesh is in order to extend the WIFI signal.

i need the router where it is, cause i need to extend the wifi to all the house.

it worked with ADSL modem, should work with cable mode. will be nice to get someone who know the correct set up and settings

thanks

It's not possible to do what you are trying to do. You cannot have two routers on the same LAN sharing the same subnet. You can set the modem to bridge mode and use your own router if that has better functions than offered by the modem. Or you can turn off all router functions on your router and connect it to the modem (ethernet or wifi) and use your router as an access point. 

 

You cannot have two dhcp servers and other router functions competeting with each other. One router and a bunch of access points is fine or one bridged modem, one router and a bunch of access points is also fine. 

ok but if someone can try to exlpain me what exactly to configure on the router. i dont care about dhcp here or there, i just want things to work.

i will say again what i had with the ADSL modem, and i want same to work with the cable modem.

2 pc's connects with cable directly to the modem, the router was connected to the modem as well with cable , and had the wifi funcion only. 

 

all mobile devices were connected to the router by wifi, and the 2 pc's were connected to the modem with rj45. it was work like that.

im not sure about if the ADSL modem was as bridge mode or not, but might be. anyyway i had internet all over my house. 

 

how can i setup the cable modem and the same router i have from before, to work togther. i cannot connect the pc's to the router, they must be connected to the modem.

i dont mind , if possibe, that only the modem will have DHCP, and provide IP's to the mobile devices as well. 

 

thanks again

To get close to your setup, you will need two routers and your modem. Cable to modem, modem to first router, first router attach the PC and the other router (no WIFI), second router is your WIFI router. 

Google "modem and two routers" for set up. 

 

Another option is Cable to modem, Modem to router with WIFI and PCs, and an extender to get the missed WIFI spots. 

 

If it were me, I would look into setting up a mesh network at that is the latest and most flexable. Google "mesh network vs router" 

 

 

thanks i udnerstand. 

so if i use cable modem, i have only the 2 optiones you mention here?. as on adsl modem i had it by just modem and router and its work just fine.

 

anyway, i might have another router over here i will try to the first option. i have a switch , that for sure, but it wont help me? 

modem -> switch -> router

the switch to connect the pc's and the router for wifi devices 

 

thanks

There is also a common thing called a repeater which is another option but since you have the cable in place, an extender is a better option.

i come to understanding that i can do it like this:

configure the router to be in the same subnet mask as the cable modem, but outside the cable modem DHCP.

disable DHCP on the router and configure it as bridge.

i can connect to cable modem to the router to WAN port. 

 

if you think this setup might work, can you explain me how i configure it on my ac1750?

as i didnt understood if i should select Dynamic IP / Static IP/ PPPOE on the router?

and where exactly should i configure the IP or default gateway of my router.

i know where to disable the DHCP of the router. but how to make it bridge? 

 

thanks!