@Caprichoso The Subnet is set by the 255.255.255.0 or 255.255.252.0.  The meaning of 255 means that that triplet needs to be the same 192.168.0 and 10.0.0 are not the same.

You should be able to access the Comcast gateway with 10.0.0.1 have you tried?

What it is specifically referring to when you change the IP from 192.168.0.1 to 10.0.0.1 is that the DHCP server is not yet changed from 192.168.0.x - 192.168.0.xxx to 10.0.0.x - 10.0.0.xxx.

But it is not a good idea to set the LAN IP to the same as the Comcast gateway otherwise you'll lose access to the gateway.

  @Caprichoso 

Thanks.  Not sure what you are saying.  I know how netmasks work.

Yes, the GE800 does access the internet via the 10.0.0.1 gateway.

The problem is that I can't change the DHCP server to serve addresses in the 10.0.0.x address range.  I get the error message "WAN IP Address and LAN address cannot be in the same subnet".  If I change the WAN address I get the error "The IP address pool and LAN IP address should be in the same subnet"

I have a TON of IOT devices which are on the 10.0.0.x network on another router.  I simply want to rename the IOT network on the GE800 to the same SSID as the old router so that when I turn it off the devices connect to the network.  I don't want to have to go to each device and reassign their network SSID.

Turned off the DHCP server.  Still get the message when try to change the LAN address "WAN IP and LAN IP address cannot be in the same subnet".

Sorry about the formatting.  Options don't work.

  @Caprichoso 

Well, that's exactly what it is trying to enforce.  It's just explaining why it doesn't allow you to change it.  You don't want your WAN to become part of your LAN nor do they want your LAN to become part of their network...

There are local IP addresses that many routers use....

In this case it is suggested to change the gateway to Bridge mode, or IP Passthrough.  Bridge mode disables the DHCP server and passes the WAN IP to your GE800.  The GE800 will get a proper WAN address assigned to its WAN port and since it is not 10.0.0.xxx will allow you to change from 192.168.68.1 to 10.0.0.1.  Don't forget to change the DHCP server range to match or it will complain...

  @Caprichoso 

Or more specifically the gateway and GE800 are both trying to service a Local Area Network at the same time.  They will avoid being on the same subnet as such.  This creates a double NAT which affects some services such as gaming in an undesired way....

Thanks for the replies.

Part of the issue is I don't completely understand what the LAN address is.  

The modem has both IPV4 and IPV6 mac addresses.

It also has an IPV4 address of 10.0.0.1

Put the modem in bridge mode.  Address is 10.0.0.1.  

Get the same error messages when I try to set the LAN address on the GE800 to 10.0.0.1.

Note that the BE800 is connected to the modem via a 10 GbE switch and and Cisco firewall.

Besides the issue of not having to reconfigure all of the IOT devices network connections, my network discovery app Fing only sees devices on one network.  If I have both the 10.0.0.x and 192.168.0.x networks in play then it will only see one of them without my having to change my Mac network settings.

The Netgear router I am trying to replace is set to access point mode, getting the IP addresses from the modem.  Since the TP-Link has excellent usage statistics (devices, apps) when devices use it's assigned DHCP addresses I want it to be the default DHCP server, unless there is another way to get statistics if the DHCP server is elsewhere.