Re: CM1100 Bridge Mode

KFT · ‎2020-05-06

Can the DHCP server be turned off? Can the IP address provided by the cable company be bridged to my attached router?

Is there an advanced configuration utility or screen to accomplish these tasks?

Having double NAT seems to be causing problems. My current docsis 3.0 modem is configured to (Bridge Mode) to pass the assigned Spectrum IP address to my router. This configuration passes all ports to the router, preventing double NAT translation and porting problems.

Is there a DOCSIS 3.1 modem from Netgear that will accomplish the roll of a simple modem interface?

plemans · ‎2020-05-06

?

I'm confused. The cm1100 is a simple modem with no dhcp or even bridge mode. It is a basic modem with the only option to change in it is being regular mode or port aggregation (combining 2x ethernet ports).

KFT · ‎2020-05-06

Why does it serve up 192.168.100.1 as it's IP address? When I connect a single computer to it, the computer gets a dynamic address assigned as 192.168.100.10. So my assumption is that there is a DHCP server providing the address to the computer. If it were simply a modem it would pass the spectrum address of 72.31.120.X or something similar.

So I assume that there is also a NAT translator as well.

plemans · ‎2020-05-07

Your isp assigns 1 public ip address to the modem. If there's no router, the device can use that 1 address.

If you want more than 1 device hooked up, you need a router.

maybe if you tell us what you're trying to do, we can better help you.

FURRYe38 · ‎2020-05-07

As mentioned by @plemans CM model modems do not have a built in router whatsoever!

The 192.168.100.1 address you see is a default modem web page address used to access the modems web page only.

If you connect a PC up to the modem, the PC will see this address for a short time. Then after the PC will get the public IP address given by the ISP. When you connect a external wifi router to the CM modem, the router will also get the public IP address given by the ISP, it won't get the 192.168.100.1 address. You can still access the modems web page using 192.168.100.1 thru the connected external wifi router.

@KFT wrote:
Why does it serve up 192.168.100.1 as it's IP address? When I connect a single computer to it, the computer gets a dynamic address assigned as 192.168.100.10. So my assumption is that there is a DHCP server providing the address to the computer. If it were simply a modem it would pass the spectrum address of 72.31.120.X or something similar.

So I assume that there is also a NAT translator as well.

KFT · ‎2020-05-07

I have a pfSense router with DYNDNS running to allow a website and other services on our network. If the WAN side of the router is assigned the 192.168.100.10 address from the CM1100 modem, how will this properly resolve? It is my understanding that I need the IP address from my provider to get to the router to get properly reported to DYNDNS.

FURRYe38 · ‎2020-05-07

The device you have connected on the CM modem should get a ##.##.###.### address. It won't get a 192.168.100.1 address. That is already hard coded to the CM modem. The modem will pass thru the public IP address after a router or firewall is connected. Be sure to contact the mfr of your router or firewall for help and information on connecting, setup and configuration of the device with a modem.