Setup for AT&T router

Customer has a Motorola NVG510 router that was installed by AT&T when they upgraded them to Uverse.  They are a small office, but they keep getting errors about invalid IPs, and they run out of IP addresses.  They have had AT&T get online with them in the past, only to say "it is fixed" when it clearly is not.

I stopped by today and they asked me to look at it.  I am no expert--which is why I am asking these questions today--but I saw where the router was configured for "Private" addresses only, in a range of something like - .170, and those addresses are indeed what was showing on their PCs when I did an IPCONFIG.  So, I changed the router settings to utilize what they call "Public" addresses, and I set a more typical range of - .250.  I saved the settings and reset the router.  After rebooting each computer, I was getting IP addresses of 192.68.1.x on each computer, and they could see their shares across the LAN just fine.

But the problem comes into play with internet access.  We could get on yahoo just fine--maybe because they are tied to AT&T??--but any other web page would either fail, or delay for the longest time, and even if we got on their main page, we could not browse to other links on the site.  In addition, their email software would no longer send or receive.

The customer says that in the past it has taken them hours to get a person on the phone at AT&T, so they had me set it back to those five "Private" IP addresses in the router, and now all is working like it used to.  But while I'm here, I'm wondering if this "rings a bell" for anyone, where you could suggest setup steps I could try in order to make it all work right using a full range of 192.168.1.x addresses.  TIA
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JohnBusiness Consultant (Owner)Commented:
The best suggestion I have (and I do this all the time) is to put the router in Bridge Mode and put a small (but good) router in front of it. Now the user will get a private address (192.168.1.x or like) and the ATT router will happily keep the same external IP address. This should work just fine and the expense is nominal.

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The "private" and "public" terms are getting mixed up here.  192.168.x.x is private as it is not allowed on the public internet.

Where are you setting these five addresses?  In a simple network these are the basic settings you should need:

WAN (internet) IP address, Netmask, Default Gateway, and DNS (done automatically with DHCP if you have a dynamic IP from AT&T or manually if you have a static IP).

LAN (local) IP address (something local such as 10.x.x.x or 192.168.x.x) and NetMask, DHCP Server enabled, DHCP Range (for example, if your router LAN address is, set DHCP range to to

If you can't get to the internet with a workstation, run the following and post the results:


It sounds as if you were right on track when you set up the 192 addresses but that there was something else going on that was giving you internet access problems.  The results of the tests above should give a clue about that.
Dr. KlahnPrincipal Software EngineerCommented:
The customer's assigned range of - .170 suggests that they are paying for (or perhaps getting even if not paying for) five static IP addresses.  Trying to expand that block of addresses won't work because it's on a netmask assigned to AT&T for one of their CIDR blocks, and the AT&T routers wouldn't route unassigned (viz., non-paid-for) static addresses to the customer's router.

Unless the customer requires static IP addresses, I'd have the customer contact AT&T, drop the static IP subscription, go to the usual single dynamically assigned IP, and put a second router behind this one.  The customer can then attach as many devices as they want to the private LAN behind the second router, and you have two layers of firewall.
JohnBusiness Consultant (Owner)Commented:
@sasllc  - Thanks and I was happy to help.
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