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What does -tnn mean in tcpdump -i eth0 -tnn dst port 80 -c 1000. I didn't find -tnn on the man page, and I didn't find it on the Internet. Can anyone explain it to me?

1 Answer 1

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You can often combine options into one combined one to make typing easier.

In this case:

-nn Don't convert protocol and port numbers etc. to names either.

-t Don't print a timestamp on each dump line.

This also implies

-n Don't convert host addresses to names. This can be used to avoid DNS lookups.

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  • Thank you, but it's weird that -nn isn't shown in my linux tcpdump man page.
    – Searene
    Oct 2, 2015 at 13:27
  • I see it on EL6, EL7, but not on Ubuntu 14.04
    – Sven
    Oct 2, 2015 at 13:34
  • tcpdump from tcpdump.org doesn't have -nn - either you specify -n, in which case none of the conversions to names happens, no matter how many ns you have, or you don't specify it, in which case tcpdump tries to do all of the conversions. Perhaps the Red Hat/Fedora people hacked tcpdump to care how many times you specified n.
    – user137177
    Oct 2, 2015 at 18:50

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