Just got fiber installed in our house however we still have our cable internet until Monday.

I am having trouble passing my AT&T fiber modem through my UniFi system. I can bypass my USG and it works fine, but if I go into my USG WAN port I can not get internet through.

Setup is modem-USG Pro - UniFi 24 port switch- UniFi 16 port Poe switch- cloud key on Poe switch.

Any thoughts on what to do here?

Somewhat of a long shot, but you may need to roll back the firmware a few versions.

Earlier this year I got frontier fiber and my ubiquiti edge router x wouldn't pull an IP from frontier. Worked just fine with Suddenlink and my backup Netgear worked just fine with frontier. Rolled back the firmware a few versions and it finally picked one up.

May not be the solution, but possibly worth a shot.

I don't have your particular setup, but you may want to Google your issue. I have come cross a lot of posts on other sites with AT&T gateways not allowing true IP passthrough.

Have you tried using IP passthrough on the gateway set to the USG device? I have the same setup with an Arris AT&T gateway.

So I figured out what it was. I had IP Passthrough set up from my AT&T modem to my UniFi USG. However the zip address range from AT&T was 192.168.1.1:24 so I had to change the USG to assign IP address starting with 192.168.2.##

Not tech savvy enough to understand why that works, but it did so I'm happy with it!

Thank y'all for ideas to look for!

ForeverAg said:

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So I figured out what it was. I had IP Passthrough set up from my AT&T modem to my UniFi USG. However the zip address range from AT&T was 192.168.1.1:24 so I had to change the USG to assign IP address starting with 192.168.2.##

Not tech savvy enough to understand why that works, but it did so I'm happy with it!

Thank y'all for ideas to look for!

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They can't be on the same network. You basically had two streets right next to each other with the same name and houses numbered the same.

I have this exact setup, and your solution is the correct one.

Enable IP Passthrough, which gives your USG the external address assigned from ATT. You need different networks for the modem and the USG to hand out. Despite the USG getting the public IP, it still has a route for the modem's internal network.

My USG is a 10.x.x.x network, and my modem is 192.168.1.x/24. As Average Joe said, if they are providing the same network it's like having two streets with the same name and numbering right next to each other.

Does anyone running ATT Fiber through their unifi notice the speeds slowing down? I'm not super knowledgeable on network setups but it seemed like it slows it down through the USG and then even more through the switch.

sanitariex said:

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Does anyone running ATT Fiber through their unifi notice the speeds slowing down? I'm not super knowledgeable on network setups but it seemed like it slows it down through the USG and then even more through the switch.

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I don't know what unifi is but a couple of years ago there was a known firmware issue with the Pace gateway/modem's that AT&T shipped out for their gig fiber customers. If you tried to use your own wifi adapter in pass through mode with the AT&T device it would dramatically reduce bandwidth to the point that you were forced to use the Pace as both gateway and router. IOW, no one could use their own wireless device unless you used an older firmware version before the break was introduced.

It took them over a year to fix it. Ridiculous.

You might be having a similar issue here. I would check the AT&T forums and see if you can find others talking about this.