T-rev's Blog

41 2013-03-29 04:50 How to set up your router behind an AT&T gateway

I'm trying out AT&T "U-verse". They force you to use their "Gateway" device, which is a combination DSL modem/NAT router/ethernet switch/Wireless AP. (Mine is a Motorola NVG510. The WAP seems to be a 2.4 GHz -bgn.) This is an issue for me because I have already have a (much better) router with several port-forwarding and iptables firewall rules, dynamic DNS, etc., and I had no desire to mess with my setup. I just wanted an internet connection for my existing LAN.

I was planning just to put my router in a DMZ, and a couple google probes into the topic turned up not much beyond some forum posts suggesting the same. Browsing through the router's config options, it wasn't readily apparent on the "NAT/gaming" page how to enable a DMZ, but I never had to try, because fortunately the next page was promisingly titled "IP Passthrough". The help in the margin said: "Passthrough: Allows the device's public IP address to be assigned to a single LAN client." Which is exactly what I wanted.

What I did:

1. disable the gateway's wifi
(Home Network -> Wireless)

2. disable the gateway's IPV6
(Home Network -> Configure)

3. [if necessary] change the gateway's LAN subnet to be separate from you existing LAN.
(Home Network -> Subnets & DHCP: in "Device IPv4 Address" and "DHCPv4 Start Address" and "DHCPv4 End Address" change .1. to .x. where x is your favorite number from 0 to 254)
Note: I first tried to use a 10.x.x.x subnet but it was disallowed.

4. enable Pass-Through
(Firewall -> IP Passthrough: Allocation Mode "Passthrough"; Passthrough mode "dynamic")

5. connect existing router's WAN port to one of the Gateway's LAN ports

6. unplug the power from everything for a few seconds

Everything worked immediately. I didn't change a single thing in my existing setup. I may still configure some static DNS servers, as DNS is currently being proxied through the Gateway, but it seems to be working well enough so far.


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