I am watching my ip6table and observing an icmp packet arriving and getting dropped at the rate of 1 per second. I am trying to find out what that message is about. I tried using tcpdump (it is definitely not an echo since I explicitly allowed that):

tcpdump 'icmp[icmptype] != icmp-echo'

0 packets captured
0 packets received by filter
0 packets dropped by kernel

As can be seen, I am seeing nothing. I have also tried logging it with iptables without any success. Any ideas?


Filter 'ip6 and icmp6' is all that works for me.

According to the manpage, tcpdump doesn't support upper-layer filters on icmpv6; at least with my version.

tcpdump version 4.5.1 libpcap version 1.5.3

  • Wonderful. I didn't know how to filter. Thanks for teaching me :) – Question Overflow May 14 '14 at 11:56

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