Nfdump is a set of tools to collect and process NetFlow data. It's fast and has a powerful filter pcap like syntax. It supports NetFlow versions v1, v5, v7, v9 and IPFIX as well as a limited set of sflow. It includes support for CISCO ASA (NSEL) and CISCO NAT (NEL) devices which export event logging records as v9 flows. Nfdump is fully IPv6 compatible.