I have been experimenting with IPv6 and tcpdump libpcap over the past several weeks and here are some of the filters that I have found working for me to look for certain types of IPv6 traffic. tcpdump and IPv6 still has some limitations but it is still able to zoom in on some of the data you might be looking for. Here is the list of libpcap filters:

IPv6 and TCP
tcpdump -nr ipv6_traffic.pcap ip6 proto 6
tcpdump -nr ipv6_traffic.pcap ip6 protochain 6

IPv6 and UDP
tcpdump -nr ipv6_traffic.pcap ip6 proto 17
tcpdump -nr ipv6_traffic.pcap ip6 and udp

IPv6, hostIPv6 and host fec0:0:0:bebe::2
tcpdump -nr ipv6_traffic.pcap ip6 host fec0:0:0:bebe::2

IPv6, host fec0:0:0:bebe::2 and TCP port 22
tcpdump -nr ipv6_traffic.pcap ip6 host fec0:0:0:bebe::2 and tcp port 22

IPv6, host fec0:0:0:bebe::2 and everything except TCP port 22
tcpdump -nr ipv6_traffic.pcap ip6 host fec0:0:0:bebe::2 and not tcp port 22
tcpdump -nr ipv6_traffic.pcap ip6 host fec0:0:0:bebe::2 and protochain 6 and not tcp port 22

IPv6, host fec0:0:0:bebe::2, and all traffic to destination port TCP 22
tcpdump -nr ipv6_traffic.pcap ip6 host fec0:0:0:bebe::2 and tcp dst port 22

IPv6, host fec0:0:0:bebe::2, and all traffic from source port TCP 22
tcpdump -nr ipv6_traffic.pcap ip6 host fec0:0:0:bebe::2 and tcp src port 22

If you have tested other libpcap filters not listed here and would like to share them, post them in the comment form or email them via our contact form.

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Guy Bruneau IPSS Inc. gbruneau at isc dot sans dot edu