Weird issue I'm facing currently! There is nothing running on port 80.

Still curl gives 404 page not found. I can telnet to port 80 and even start a container exposing port 80 (host). But no requests reaches the container!

Any idea what might be going on? How do I debug this?

$ netstat -tulpn | grep :80
tcp        0      0  *               LISTEN      -                   
tcp6       0      0 :::8000                 :::*                    LISTEN      -                   
$ curl localhost
404 page not found
  • 6
    Please provide output of iptables -vnL -t nat or nft list ruleset ip as theres possibly a internal nat redirect causing that behaviour. Sep 8, 2021 at 9:44
  • 1
    It was indeed because of iptables rule. I had installed k3s which configures some iptables rules. Uninstalling it solved the issue.
    – Shinto C V
    Sep 9, 2021 at 10:51

1 Answer 1


In addition to Matthew's comment suspecting internal nat redirect

  • iptables -vnL -t nat or nft list ruleset ip

perhaps you could directly inspect port 80. These are some of the ways to do that:

  • ss -4tlnp -o state LISTENING '( sport = :80 )'
  • lsof -i:80
  • do a verbose tcpdump
  • do a verbose portscan with nmap
  • or, be even more explicit when testing with curl, ie curl -v http://localhost:80
  • 1
    I would add curl with -v option to the top of this list.
    – Tomek
    Sep 9, 2021 at 6:01

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