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tcpdump

what's the meaning of tcpdump option vnn

Here is a tcpdump command:

# tcpdump -i eth0 -vnn  udp

-i means interface eth0 is the interface name udp means upd protocol, but, What's this option[-vnn] meaning?

Solution

  • '-vnn' is the same as specifying -v and -nn as two separate options. From the tcpdump manual:

    -v When parsing and printing, produce (slightly more) verbose output. For example, the time to live, identification, total length and options in an IP packet are printed. Also enables additional packet integrity checks such as verifying the IP and ICMP header checksum.

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

    Note that -nn implies -n as well.