IPv6 snooping captures the IPv6 traffic and helps in populating the binding table. It gathers addresses in control messages such as Neighbor Discovery Protocol (NDP) or Dynamic Host Configuration Protocol (DHCP) packets. Depending on the security level, it blocks unwanted messages such as Router Advertisements (RA) or DHCP replies. This feature is a pre-requisite to the remaining security features mentioned here. https://www.cisco.com/c/en/us/td/docs/routers/7600/ios/15S/configuration/guide/7600_15_0s_boo k/IPv6_Security.html