Can't connect to UI3 while on LAN

[Lee No Shiro]

So I just switched from Comcast to ATT Fiber on a 2g connection after having Blue Iris for over 2 years.
Now whenever I try to connect to the WAN address for the UI3 the connection is either very slow or refuses to connect. This was not an issue at all while I was on Comcast and on my Asus RT-AC68U. Now I'm on the ATT BGW320-505.
I've tried disabling all firewall options and this issue still occurs.

Blue Iris can't connect on LAN Network

I've been running Blue Iris 4 on my PC for years with no problems. Switched ISPs from Comcast to ATT Fiber yesterday. I was able to get cameras functioning without a problem. I was able to go into ATT settings an open up port 81. On the mobile Blue Iris app, if I am not on Home Wifi I can...

ipcamtalk.com

Pretty much having the same issues as this post but I'm not using the app, just the UI3. This occurs only on LAN/Wi-fi on either phone or computers. "Outside" internet connects and functions perfectly fine
Am I just missing some setting on this ATT router?
Any help is very welcome as my family not very tech savvy and telling them that they will have to use a different page/address to view UI3 while at home will be a difficult battle

 

[The Automation Guy]

I want to make sure I understand your situation correctly.....

You want to use a single, public IP address in your UI3 setup so that you can view the cameras both while on the local network and remotely while you are away from your network. Right now, when you try to use the public IP address while on your local network, things are really slow. Is that correct?

Using a public address to access a local lan device is not as simple as it sounds. It's not surprising that it isn't working with the new setup. Basically you have a "hairpin NAT" - where a request for the public IP needs to be directed back into the local network. You'll have to determine if your new equipment is capable of handling a "hairpin NAT". Right now it clearly is not set up to handle this situation correctly.

Here are some results from googling "ATT BGW320-505 hairpin nat". Unfortunately I cannot access the ATT Forums from my current location to see what the recommendations are to fix it.

Google Search

www.google.com

 

[Lee No Shiro]

You want to use a single, public IP address in your UI3 setup so that you can view the cameras both while on the local network and remotely while you are away from your network. Right now, when you try to use the public IP address while on your local network, things are really slow. Is that correct?

Yes, this method had worked before on my old setup. I forgot to add that on the ui3 logs, whenever someone trys uses that public ip address when they are on LAN, it shows up as they are logging in directly from the gateway ip 192.168.1.1
It wasn't like this before.

Basically you have a "hairpin NAT"

Thank you!! I've been trying to figure out what this issue would be called to better search for a solution. I'll have to do more research when I get home but thank you for pointing me in the right direction.

 

[Lee No Shiro]

So just updating in case anybody comes across this issue as well. So yes, it's a matter of nat haipin (or nat reflection, nat loopback or whatever else it is also called. The att modem/router BGW320-505 does not support that function so my solution was to get a router that does and just put the BGW320-505 in passthrough mode. There seems to be other options such as setting up DNS and other stuff but I opted for the router.

I forgot to add that on the ui3 logs, whenever someone trys uses that public ip address when they are on LAN, it shows up as they are logging in directly from the gateway ip 192.168.1.1
It wasn't like this before

Well, it also does this with the new router so maybe I just wasn't paying attention to it before.