@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.

  @Caprichoso No worries.  That's what the forums are for to get answers....

Each device gets assigned an IP address.  For IPv4 xxx.xxx.xxx.xxx.  Every GE800 manufactured has the exact same default settings.  So imagine your neighbor has a TP-Link router and it also has the same.  Local Area Networks of TP-Link routers tend to have local IPs 192.168.68.1.  The router's DHCP server assigns Local IPs typically 192.168.68.2 - 192.168.68.254 (with a subnet 255.255.255.0).  So the router also Network Address Translates so web traffic is sent to the proper device...

The 10 GbE switch and Cisco firewall, what are they doing?  Seems like you have a complicated setup and I'm not sure how to resolve those two items.  So modem - 10 Gb switch - Cisco - GE800?  What are the models of the switch and firewall?

Please don't confuse MAC address which is supposed to be unique to each device with IP address...

Anyways the goal is to transfer the routing functions to the GE800.  The modem has to be a combined modem/router unit if it has a DHCP server, aka gateway.  Do you mind sharing what model it is?  What is your ISP?

  @Caprichoso The easiest thing to do starting would be to connect the modem/gateway directly to the GE800.  Remove the switch and firewall if possible...

The problem with that is then internet access isn't protected by the Cisco firewall.

Is there any other way?

Edited: won't work as the Comcast XB8 modem doesn't have any 10 GbE portsl

  @jzchen 

1.  The Comcast XB8 modem doesn't have any 10 GbE ports    By connecting all of my 10 GbE devices via the switch they are able to communicate between themselves at 10 GbE speeds.

2. WiFi 7 devices connecting to these devices,  iPhone-GE800-switch-NAS for example, are able to get the fastest speeds that way.

3.  If we assume the LAN network is the 10.0.0.1 modem I don't understand why there would be a conflict.  The GE800 would just assign addresses in the 10.0.0.x network, but would be setup to not use 10.0.0.1.  The XB8 would be in bridge mode, DHCP server disabled, so there should be no conflicts.

NetGear Switch XS708T

Cisco RV340 VPN Router

Comcast XB8 modem

XB8 > Cisco RV340 > XS708T

XS708T is connect via 10 GBe connections to a Mac, 2 NAS units and the GE800

  @Caprichoso Thanks for sharing the models, that allows me to find out what they are capable of, and so I can help sort things out...

The XS708T can simply be moved to the LAN side of the GE800.

The RV340 has reached its End of Life.  I would no longer rely on it to protect my network and suggest you stop using it for such purpose.  I am typically not allowed to link webpages to my posts, but you can search Cisco RV340 End of Life Notice, select the appropriate link, and confirm SW Maintenance Releases stopped over 3 years ago on October 28, 2022.

The good news is you can have the GE800 do the firewall function.  The not so good news is that there's some sort of subscription fee associated with it as it is provided by Norton per my understanding...

The XB8 is a nice WiFi 6E unit.  I was just watching a YouTube video where a guy was replacing his XB7 with the XB8.  Still the GE800 is nicer.  I recommend:  XB8 - GE800 - XS708T - 10 GbE devices.  You can connect Ethernet devices 2.5 Gb or lower directly to the GE800 2.5 Gb Ethernet ports.  Still believe best practice is to change the XB8 to bridge mode.  (Haven't found/confirmed this is possible).