Is there a way to test if port is being blocked by ISP rather than something being wrong with router/firewall settings? I am trying to use DVR in my house but ports are beeingg closed no matter what I do. I set router port forwarding and test ports and they are still closed. I am unsure if i am doing aomething wrong or this is ISP issue.

  • 1
    Your question is unclear. Are you trying to access something from outside your home network? What port forwarding rules have you set? For what services?
    – user931000
    Mar 27 '19 at 10:46
  • 1
    Does your router/firewall have a "packet capture" program (e.g. tcpdump)? Does your router/firewall have a global (public) IP address?
    – user1686
    Mar 27 '19 at 10:54
  • Is any answer a solution? Nov 12 '19 at 14:06

Your ISP might be blocking some ports, like typical filesharing ports, or Port 80/443.

One reason to block port 80/443 might be to block access to wrong configured routers which open their web interface to the public.

Another reason might be, your ISP does not want you to use your soho internet connection to host a website.

You can try a random port, just make the source port of your forwaring 1234, and the destination port 80/443.

Another possibility is, that your internet access is also behind another NAT router at the ISP, because it might have run out of IPv4 Adresses, as they are very rare today. This allows the ISP to run multiple users with one public ip.

  • 1
    Did you leave something out of your penultimate paragraph? The last sentence appears to belong to the next paragraph. +1 for bringing up CGNAT. Mar 27 '19 at 13:44
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    Actually I mixed something. Mar 27 '19 at 14:31

You can check the ISP ports blocking on this page

  • Suggestion: To increase the usefulness of your answer, update the link text to show the actual link you are pointing to - so that readers can see where you are sending them (e.g. use: canyouseeme.org). Also, if there is a brief excerpt from their website with instructions, consider pasting that text directly in the answer (and of course, do credit them as providers of the content).
    – qxotk
    Mar 27 '19 at 18:52
  • Yes ports are not open if i test it using canyouseeme
    – Stribor
    Mar 27 '19 at 21:14
  • 1
    @condiosluzverde, he got what he needs. short and simple
    – Jordan
    Mar 28 '19 at 19:16
  • @Jordan I see where you're going with that, and I am not saying you are right or wrong - just trying to be helpful. Observation: at the time of writing this comment, this question has 38 views, the question has not been voted up, your post has not been selected as the answer, nor does it have any up votes.
    – qxotk
    Apr 22 '19 at 20:31

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