New Cable modem and IP router scheme

Skeeterslint667
Star
Dec 08, 2019
Clan_Hunter wrote:
Sir,

will my LAN IP addressing scheme be defined by the IP address of this DOCSIS modem and it's default address?

I have printers on my network that use Google Docs to print documents. I don't wanna go thru setting all of that up again but prefer to keep my IP addressing scheme.
Can you explain the relationship of the cable modem to the router? Even though it has an IP address my router doesn't know what that IP is, it just receives an internet connection . I don't have to define the cable modem in the router setup.

The address the modem has is just so you can get to it from the internal network. Your better off not using the 192.168.100.X subnet internally and using something else just so it doesn't conflict with the modem itself.
- antinode
  Guru
  Dec 09, 2019
  >    Replacing what?
  
     Do you ever answer questions, or do you only ask more?
  
  > Well, I agree but the router can be the IP address you define. Why
  > won't my network take the configuration that I define my network by?
  > [...]
  
     It "can be the IP address you define" unless that address conflicts
  with some other entity on your network. Like, for example, a DOCSIS
  modem.
  
  > [...] I don't know if the cable modem has a relationship with my
  > router but something isn't playing nice.
  
     That "something" is you. You seem to insist on choosing a LAN IP
  subnet for your router which would conflict with the standard address
  for a DOCSIS modem. Perhaps your previous modem was a different type
  (DSL?), or your previous router didn't care, but Netgear routers
  generally do care.
  
  > will my LAN IP addressing scheme be defined by the IP address of this
  > DOCSIS modem and [its] default address?
  
     Not "defined", but certainly _limited_.
  
  > I have printers on my network that use Google Docs to print documents.
  > I don't wanna go thru setting all of that up again but prefer to keep
  > my IP addressing scheme.
  
     I don't understand what Google Docs has to do with anything, but
  what, exactly, do you expect to need to reconfigure?
  
  > [...] Even though it has an IP address my router doesn't know what
  > that IP is, it just receives an internet connection . [...]
  
     I'm not sure that you know what your router knows or doesn't know.
  
  > [...] I don't have to define the cable modem in the router setup.
  
     That's true, but that doesn't mean that the router will (or should)
  allow you to use the "192.168.100.*" subnet.
  - schumaku
    Guru - Experienced User
    Dec 09, 2019
    A router does need to run two different subnetworks on the WAN/Internet interface and on the LAN/WLAN interface.
    
    As the 192.168.100.0/24 subnet is the default internal subnet (not only) for Netgear cable modem and cable routers the second R6xxx does automatically change the effective internal LAN subnet as a courtesy (and because it can't act as a router with oth interfaces on the same subnet).
    
    Now the bigger and not discussed issue here is that you have to NAT routers - the CM600 and the R6xxx. Either run your local network only from the CM600 (and reconfigure the R6xxx as a plain wireless access point as per the documentation if possible) or re-configure the CM600 as a plain cable modem/bridge and only establish one wired connection from the CM600 to the R6xxx WAN/Internet port. Now you can re-configure the R6xxx again to that 192.168.100.0/24 subnet. One constraint remains: Should eg. following a power failure the CM600 won't be properly connect and configured by the cable TV company headend the CM600 (and most other cable modem/routers) will locally configure the network to that very same 192.168.100.0/24 network - and the R6xxx will do it's smart-a** re-configuration of the LAN subnet again.
    
    I would opt to go away from this 192.168.100.0/24 network for your LAN once time is permitting to re-configure all LAN devices - yes, it will take some time.

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New Cable modem and IP router scheme