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Setting up Cisco Router behind the AT&T 3801HGV Router


Setting up Cisco Router behind the AT&T 3801HGV Router

Before I got new U-Verse service (Internet & TV) 2 weeks ago, I had a home network set up with a Cisco Linksys E2500 dual-band router.  I have a Dell desktop PC running Windows 7 and 10 wireless devices.

I followed another forum members directions pertaining to bridging the 2Wire router and the Cisco router, changing the IP address of the 2Wire router and turning off the wireless function.  I set these up so that the 2Wire router was behind the Cisco router.  Everything worked just the way I intended until today.

There was a power failure at my home yesterday from an outside source.  The 2Wire router and the Cisco router returned to their factory settings for the most part.

Now, I cannot change the 2Wire router's IP address.  I have tried it several times and cannot get the router to respond.  

There are other parts of the 2Wire router that will not let me change (system password)

Has there been  any system changes that would effct the 2Wire router?  Should I reset the 2Wire router to it's factory settings and start again?

Thank you for your help.

Message 1 of 22

Accepted Solutions

Re: Setting up Cisco Router behind the AT&T 3801HGV Router

Not sure if we're just talking semantics, but the Cisco should be bhind the 2WIRE. You can follow these directions if you'd like to try again. If your changing IP addresses it should be on the Cisco not the 2WIRE.




This is what I did to use an "internal" router (when I had Uverse)(3800 gateway). I set my "internal" (Cisco) router to use DHCP for the WAN address, plugged it's WAN port in to a LAN port on the 2WIRE, reboot the "internal" router, let the 2WIRE assign a local address to the "internal" router and then set that address to the DMZ in the 2WIRE's management interface. When I go to the "internal" router's management interface it shows as having the same WAN, gateway, and DNS addresses that the 2WIRE uses.

I set the "internal" router to assign addresses to "my" side of the network in a different IP range than what the 2WIRE uses (192.168.2.* instead of 192.168.1.*) but using the same subnet mask ( My internet works fine with no interuptions and local network tasks (back ups, streaming, etc.) work as expected. I can also still access the 2WIRE from "my" side of the network when I need to without having to change any network settings or swap any cables. Leave DHCP running on the 2WIRE. You do not need to disable the firewall in the 2WIRE as the DMZ will open a pinhole through it to the address you pick (your internal router). If you have existing wireless on your router that your satisfied with and want to keep, just make sure to turn off the wireless in the RG.

If you currently have your router behind a basic DSL or Cable modem, Your setup will be pretty much the same. The 2WIRE will replace your modem, then go into your existing router and change it's internet connection type to Dynamic or DHCP. Then change it's internal network IP adress and DHCP Pool and you should be good to go.



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Message 3 of 22

All Replies

Re: Setting up Cisco Router behind the AT&T 3801HGV Router

In at least some cases, inbound port 22 is blocked and reserved by AT&T for their equipment.

You can get around this in 2 ways:

1. Purchase static IPs instead of using DMZPlus. No inbound ports are blocked on static IPs.

2. Adjust the firewall on your router to have a pinhole with port translation. e.g. Inbound port 2222 to the outside IP gets forwarded to your ESXi server on port 22. Then, when you need to connect to the ESXi server's SSH port, just make a connection to your outside IP address on port 2222.
Message 16 of 22

Re: Setting up Cisco Router behind the AT&T 3801HGV Router

I ran a port scan last night...found out that most all ports are blocked...except 80 and 443...I can't connect internally or exteranlly....I may have to get static IPs...(which will be another set of stuff to deal with in terms of firewall, etc)  I am not sure that I would know how to set that up in terms of security, etc.  Most of my IT career I have dealt with NAT using a sigle IP and class C addresses....Any thoughts?

Message 17 of 22

Re: Setting up Cisco Router behind the AT&T 3801HGV Router

I have the same WRVS4400N and 3801HGV. I followed the instructions to a "T" in this post,
and everything worked like a charm. BUT, all of a sudden, today the public IP that the 3801 was pushing to the cisco router was no longer there. and the router wont get it again, unless i do a hard reset. Is there some other setting i can set, either on the router, or the 3801? I'm a networking guy, but man these u-verse routers are a pain to deal with... stuck please help!!!
Message 18 of 22

Re: Setting up Cisco Router behind the AT&T 3801HGV Router

Note, here is my firmware for each.
3801HGV -
wrvs4400n -
Message 19 of 22

Re: Setting up Cisco Router behind the AT&T 3801HGV Router



I recently added my old Cisco/Linksys E1000 router behind my 3801HGV this weekend. The main purpose was to see if my wireless cameras would work because I could never get them to work directly off the U-Verse RG after reconfiguring and trying different things like MAC filtering. They would only work wired but not wirelessly.


My setup is nearly identical in that my E1000 is set to now (instead of 1.1) When I first connected the WAN port of the Cisco E1000 to the LAN port of the U-Verser 3801 HGV, it could not be seen/detected. It was not until the IP address change that the U-Verse saw the Cisco and the Internet came back to the computer that was plugged into the Cisco (and another PC wirelessly connected to the Cisco).


My question is do I really need to enable this DMZ stuff many "router behind router" posts talk about and why? So far everything seems to work ok, internet access, VPN for work, etc and I have not noticed any problems. Unless there is stuff happening behind the scenes cluttering up the network.




Message 20 of 22

Re: Setting up Cisco Router behind the AT&T 3801HGV Router

Hi sticksdkw,


You shouldn't need to use DMZ unless you do not wish to forward each port or range for whichever applications you are using. Many sites recommend DMZ only as because it allows for all communication and traffic. This could be viewed as a security hazard for businesses so from my perspective it is best to forward each range or port for the applications being used. DMZ is great, but as the meaning implies, it lacks enforcement of any kind.

Message 21 of 22
ACE - Expert

Re: Setting up Cisco Router behind the AT&T 3801HGV Router

The DMZplus zone basically hands off responsibility to the device in the DMZplus zone.  If it handles NAT or stateful packet inspection or something like that, that's fine.  If it's just a PC without firewall software, then not such a good idea.



*The views and opinions expressed on this forum are purely my own. Any product claim, statistic, quote, or other representation about a product or service should be verified with the manufacturer, provider, or party.
Message 22 of 22
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