Cascaded Router Network Addresses

Question

In my home network, I have to use AT&T's router. It is a Motorola NVG510.

Behind this router is my personal router, a dual band Netgear TL-WDR3500 with USB ports for my NAS drives.

The AT&T router connects to the DSL line, and has its wireless radios turned OFF.

• IPv4 Address: 192.168.1.254
• Subnet Mask: 255.255.255.0
• DHCPv4 Start: 192.168.1.64
• DHCPv4 End: 192.168.1.253

My Netgear router connects directly to one of the switches on the AT&T router.

• IP Address: 192.168.0.1
• Subnet Mask: 255.255.255.0
• Default Gateway: 192.168.1.254

I want to setup the Cascaded Router feature, but to do that I need to supply the following:

• Cascaded Router Address: The IP address for the router behind this device. The Cascaded Router Address should be in the LAN Private IP subnet range.
• Network Address: The Network Address that defines the range of IP addresses available to clients of the cascaded router.
• Subnet Mask: The subnet mask that with the Network Address defines the range of IP addresses available to clients of the cascaded router.

Everything I try gets kicked out as invalid.

For the Cascaded Router Address, I always enter 192.168.0.1, since that is the defined as the router address on my Netgear router. That only leaves Network Address and Subnet Mask.

Network Address 192.168.1.253, for example, is rejected because it is not in the network address given subnet mask 255.255.255.248.

I got Cisco certified in networks about 10 years ago, but I was never able to get a job in networks. I can't remember how I am supposed to calculate the network address ranges and subnet masks anymore.

Can someone give me this information? I would also like to know how to go about calculating these for my information, just in case something changes down the road.

Answer 1

Both routers need to be in the same subnet. In your case this would mean a range of 192.168.1.1 - 192.168.1.7. This means that your routers WAN IP has to be in this IP address range.

The detailed steps are explained here:

https://forums.att.com/t5/Features-and-How-To/How-to-put-the-Motorola-NVG589-in-bridge-mode-or-as-close-as-you/m-p/3552057#M39255

Otherwise, why not dual NAT and put any servers, NAS etc. into the outside one? My RPi makes for a decent VPN and NAS.

Answer 2

Here is what I got to work.

I had to configure the subnets. What worked for me was only allowing 1 IP address:

Next, I had to configure the firewall to allow IP Passthrough:

At this point, I rebooted the AT&T router modem.

While that was going on, I used my wireless network card to configure my Netgear router. I had to change the IP address, Default Gateway and Primary DNS:

By the time I was doing all of that, the Motorola router modem was through rebooting, and HERE I AM! :)

That was a lot of work for me!

Hopefully, someone comes along later and gets some good out of it.