IP Passthrough Drops Randomly

Most likely what is happening is that the DHCP renewal process between the Gateway and your router is intermittently failing.  While the lease has expired, the router can't send traffic.  Eventually it starts a new cycle asking for a lease (vs. renewing one) and it comes back up.  Things you can do about this:

1) Extend the lease time for IP Passthrough on the IP Passthrough page.  This gives it more time to negotiate the lease; the process starts half way through the period which defaults to 10 minutes, meaning it has 5 minutes to complete successfully before it loses the lease, and the process have to be repeated every 5 to 10 minutes.  Lengthening this to a day means 12 hours to accomplish the renegotiation.

2) Change to static mode IP Passthrough; copy the DHCP-assigned information down and manually put it in your router as its WAN information.

@JefferMC @markbnj I tried both suggestions, and I am still having issues from 8:00am - 9:00am every single day. I can restart the ATT modem and the issue is fixed for 15 minutes, then I have to restart the modem again. As soon as 9:00am comes around, the issue does not appear for 23 hours. I am really not sure what has changed because I never had this issue until about a month ago.

Perhaps what is happening is some high volume traffic being sent through your router between 8 and 9 AM (a scheduled backup, perhaps) that is flooding the connection table.

I also had this issue, unfortunately i could not get it resolved so i just stuck to the same old router/modem att provides. Any updates if you got iit to work

I have tried all of these solutions with NO Resolution. IT looks like settings on the modem, perhaps in a firmware update has rendered the ability of using IP Passthrough un-usable. I have contacted AT&T support, had a tech spend 3+ hours onsite, and NO RESOLUTION, its going on 2 weeks without the ability of using my connection fully.

As of right now, I am not able to use IP passthrough, cannot access alot of my security systems, cameras, etc... And no one at AT&T customer service, technical support, fiber dept cares enough to try to figure out what is the issue. 

Sad part is, this only affects one property, and not the others I have with AT&T Fiber, all within the same city....SOOO that means there is an error on this one account, but again, no seems to be able to figure out why, or how?

@whoezdaboss  could you describe what is happening vs what you expect to happen?  Also... you did factory reset your gateway, right?

When in IP passthrough, the connection is unstable, frequent disonnections, as many time as 4 to 5 in less than 5 mins window.

BUT when you turn off IP passthrough, everything works, with the exception of port forwarding, DDNS services, hence why I have ALWAYS used my own router.

This worked beautifully since I signed up for AT&T Fiber 1000.

3 techs, 4 modem swaps, 2 fiber connection "rebuilds," 2 cleanings for reflection, multiple calls to tech support ----ALL USELESS. 

I even bought a entire new ubiquit setup! Switched to another system, Omada, same issue. Tried a old ASUS router that I had, SAME ISSUE.

• Reset the modem atleast 50+ times (No joke).
• Had the modem swaped, even the SPF that connects into the modem....
• Changed the DHCP settings to 99 day lease on the ATT modem, no change.
• Even inputted WAN IP address info into my router as static, SAME issue....

SAME ISSUE. Frequent disconnects resulting in a UN-USEABLE connection!

Any Advice? 

Which DHCP setting did you change to 99 days?  The one in the IP Passthrough page, or the one in Home Network > Subnets & DHCP.

Can you be a little more specific in what you mean by "connection is unstable" and "frequent disonnections", e. g. what do you mean by these terms... what are the specific symptoms?

@JefferMC I changed in both areas. 

I am having the same issue, my wife has had to restart the ATT modem/router at least once a day for over a month. I didn't change any settings on my personal router, I wasn't even in the country when it started happening; and my wife wouldn't even know how to login to the router nor try to. ATT had to have changed something they don't want to own up to. The only thing I know has changed is that a couple more of my neighbors have switched to ATT Fiber, so maybe it has something to do with the way their traffic and IPs are handled outside of my LAN and individual WAN connection.