HSRP version 2 with MD5 authentication is the correct resilient gateway choice because the design requires IPv6 support and protection against false hello packets. HSRPv2 supports both IPv4 and IPv6 gateway redundancy and improves group scaling compared with the original version. MD5 authentication protects the HSRP control exchange by ensuring that only authorized routers participate in the redundancy group, reducing the risk of a rogue or misconfigured device sending false hello messages and influencing active gateway selection. GLBP provides load balancing but does not satisfy the same IPv6 and authenticated hello requirement in this option set. VRRP version 2 is IPv4-focused and therefore does not meet the IPv6 requirement; VRRPv3 would be the relevant standards-based IPv6-capable version, but it is not offered.
Object tracking helps adjust gateway priority after link failure, but it does not protect against false hello packets by itself. Reference topics: HSRPv2, first-hop redundancy, IPv6 gateway redundancy, MD5 authentication, campus high availability.