Networking & Wireless forum


Network blocking DDNS

So I install surveillance video systems for commercial and residential applications. I recently noticed two customers having this issue with an xfinity modem/router. Two different model routers which I dont have at this time. The issue is as follows:

I use a DDNS client for the DVR/NVR due to dynamic IP addresses. I open up ports 80 and 8000 so it can be accessed remotely. I can access the systems remotely with no issues when I am not attached to the wireless router on the same network the DVR/NVR is attached to. When I am on the network, I cannot access the DVR/NVR when I am going through the DDNS website. If I use the IP address assigned by the router (i.e it works, but for some reason the router is blocking the DDNS website when I am on that network. I disabled the firewall and still had this issues. Comcast of course is no help on the phone and is blaming the DVR/NVR. I pretty confidant there is a setting on the router that is causing this issue.

Was wondering if anyone knows

Thanks in advance


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Clarification Request
Here's a thing.

In reply to: Network blocking DDNS

Inbound 80 and 8000 is sometimes blocked by ISPs. Test with some odd random ports.

Sorry but ISPs do make a mess of this stuff.

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In reply to: Here's a thing.

I found out the issue. Comcast does not support NAT or Hairpinning as it is called. I guess it doesn't allow you to go out of network only to come back into the network through another server. Sorry if I did not explain it correctly. I did try other ports with the same result.

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