Helping Configuring NCM1120D2

I'm having a similar problem with this gateway. Device IP entered in DMZ is not reachable from the gateway's Internet IP.

Hello @baywil,

Thank you for reaching out to us!
We understand you are looking for the assistance to setting up Internet IP for the internet Air. Let's get the help you need!
As this concern is related to Internet Air, we have our dedicated team who can assist you. Please reach them at 800-288-2020 for further assistance.
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Thank you.

Mike, AT&T Community Specialist.

It will be interesting to hear what you find out.

In reviewing the documentation there does not appear to be an option which provides IP Passthru to a LAN device which is also using the WAN IP address. The DMZ option (which is more like a default server) appears to allow passthru of all WAN traffic to a specific LAN device, but one that is using a private IP address.

Which may be indicated by the section of the GUI that the option is under (i.e., NAT Forwarding) and the recomendation "to assign a static IP address to the intended device.", which is not practical for the WAN IP address since it changes often.

@ATTHelp

I tried to call the Internet Air group at 800-288-2020 (and a list of other support numbers passed onto me by 1st level support) and I spent the next 3 hours speaking to Indians, Philippinos, and even someone from one of the Soviet satellite countries contracted by ATT. While most were able to pronounce the English words, few understood the context and of no help whatsoever. I don't recall ATT being so hard to obtain qualified support from but, they're horrible now.

As for the DMZ question, I set up the 5G gateway with a single laptop client which a dhcp-supplied IP. I then registered that as static with the gateway so it could expose it to the gateway's internet IP. I even went as far as attempting to use the gateway's virtual server to forward ports to the static ip and enabled pings from WAN. No dice - can't connect to the laptop with even a ping from the internet. Oddly, the laptop's ip remains the LAN-assigned static one vs. changing to the gateway's internet IP as is the case with the ATT DSL router I'm trying to replace.

I've run out of combinations to try in the gateway's config. As a ATT Business customer, I'm dismayed that they would send me a piece of equipment they can't support and cause a customer such desperation as to have to appeal to a community forum for help.

> Oddly, the laptop's ip remains the LAN-assigned static one vs. changing to the gateway's internet IP as is the case with the ATT DSL router I'm trying to replace.

Not odd. The device was probably not designed to support that.

The Internet Air service is likely operating similar to other AT&T cellular service, with IP addresses that change often. As such, there is limited value to doing passthru as you expect.

I am surprised that they even allow for unsolicited inbound traffic to the WAN IP address as they usually block this on their cellular networks.

If you had the device in front of you and had previous experience with DMZ and IP passthrough, this would make sense to you. 

@sparrowthejoker

Here is the end of my NCM1120D2 research and it may help you. What I found in my case was that 1) the LAN IP entered in the DMZ setting was not accessible from the gateway's WAN IP 2) The NCM1120D2 is on a Carrier Grade Nat (CGN) where the NCM1120D2's WAN IP is not on the internet but, NATs up to another IP which is on the internet (you can verify this by visiting any site that provides your internet IP i.e. whatismyipaddress.com and comparing your internet IP with the NCM1120D2 WAN IP).

The only solution I found for internet exposure with the NCM1120D2 was to run a vpn from a port forwarding service such as portmap.io (any port-forwarding service will work) where they would generated a static hostname for you that forwards port packets back to your machine running the vpn.

As for me, after ~ 10hrs on the phone over the last week unsuccessfully asking ATT for support on this issue, I'm off to another ISP. ATT used to be 1st class but, now they sub out all their 1st level support to 3rd world countries to save $$$. In my 10 hrs of phone time attempting to correct my DMZ issue, I actually felt bad for the offshore support rep who actually tried to wait with me over 20 min to get to a 2nd level support back U.S. support department - he got no special treatment whatsoever.

Bottom line for me: ATT's Internet Air works well except for users that need port forwarding or DMZ services. BTW I just saw the notice at the top of this page that the community forum will cease to exist after June 27th, 2024 - just another ATT cost savings move I guess.