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When trying to establish a TCP connection to my IP address, 192.168.1.42, netcat tells me that the host isn't authorative. That is,

[~] $ echo "Hello, world"|nc -c -vv 192.168.1.42 8080 & nc -l -p 8080 192.168.1.42
Warning: Host 192.168.1.42 isn't authoritative! (direct lookup mismatch)
  192.168.1.42 -> feross  BUT  feross -> 127.0.0.1
192.168.1.42 8080 (http-alt) open
Hello, world
Total received bytes: 0
Total sent bytes: 13
Total received bytes: 13
Total sent bytes: 0

Why?

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    Broken reverse DNS in a LAN? What does host 192.168.1.42 report? – Incnis Mrsi Sep 17 '15 at 16:47
  • @IncnisMrsi, $ host 192.168.1.42 outputs Host 42.1.168.192.in-addr.arpa. not found: 3(NXDOMAIN) – Giuseppe Crinò Sep 17 '15 at 16:52
  • OK, then fgrep 192.168.1.42 /etc/hosts – Incnis Mrsi Sep 17 '15 at 16:52
  • @IncnisMrsi, reports nothing – Giuseppe Crinò Sep 17 '15 at 16:55
  • What do you try to achieve with nc -c? – Incnis Mrsi Sep 17 '15 at 16:58
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The message

Host 192.168.1.42 isn't authoritative! (direct lookup mismatch)
192.168.1.42 -> feross  BUT  feross -> 127.0.0.1

indicates that two specified BSD Sockets calls:

  • gethostbyaddr – returns "feross" on 192.168.1.42 (IPv4)
  • gethostbyname – returns 127.0.0.1 (IPv4) on "feross"

Assuming there is no 192.168.1.42 in /etc/hosts and host 192.168.1.42 fails, it might be caused by broken setup in /etc/host.conf, by an obscure poorly documented name resolver library, or by whatever.

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