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doncaruana
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Monday, November 15th, 2021 3:24 PM

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Accessing my external IP from my internal devices

I just upgraded my gateway from an XB6 to an XB7 and I had this working before. I can access my public IP (on a specific, not blocked port) from outside my network. So the gateway is routing external traffic appropriately. However, if I try to access that external IP from my INTERNAL network, the traffic will not be get there. Basically you can't reach the external port from the internal network. I don't remember having them do anything special to get the XB5 to work. Is there a setting somewhere that I or they can change to get this to work?

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3 years ago

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EG

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109.5K Messages

3 years ago

You can't. That's called NAT loopback or hairpinning, and they have it disabled in the Comcast supplied gateway devices.

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doncaruana

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3 years ago

Well, actually, let me update this a bit. This has 4 ports on the back. I have some devices coming through a switch that's plugged into one of the ports and then my main computer which is plugged into a different ethernet port. The main computer CAN access the external IP. But the other ones cannot. I have tried every cable in every port and this is still the case. And, keep in mind, I'm coming from a Comcast supplied gateway device that I just got last year where this was all working and it is working for a device currently - so it doesn't look like it's disabled. And I didn't change any internal configurations with the gateway switch - I just plugged in the same cables into the new gateway.

(edited)

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EG

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109.5K Messages

3 years ago

O/k... If you get it figured out please post back here with the solution. Thank you. Good luck !

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doncaruana

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9 Messages

Haven't had time to mess with this again until now. Super weird still. Any individual device (laptop, desktop, anything wired) I plug in to the XB7 works fine. But if I run it through my switch (Netgear GS208) or an internal wireless router first (Netgear Orbi), it won't work. Almost like it won't route it if the actual device connected is not the one making the request. Does that make sense? I tried powering the gateway down, unplugging everything, then plugging things back in one at a time (desktop, switch, orbi), exact same behavior. I have no idea what would control this behavior and why it's different.

It sounds remarkably like this thread to me, but there's no posted solution there other than the guy who restarted everything:
https://forums.xfinity.com/conversations/your-home-network/xb7-lan-connection-tothrough-ethernet-ports-on-xb7-dropping/602daf54c5375f08cd0837b6

3 years ago

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doncaruana

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@EG - So I sorta figured this out. I have access enabled to one of my internal devices over a specific port via port forwarding. As long as that device is on a different ethernet port than the one doing the requesting, access is allowed. So essentially it is a hairpinning issue, only in regards to the specific ethernet port on the XB7.

3 years ago

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