RA guard is useful if your tcam capacity and or switching platform allows - http://tools.ietf.org/html/draft-ietf-v6ops-ra-guard-implementation-01
An older yet still a good read from Cisco on some IPv6 first hop security: http://www.cisco.com/en/US/docs/ios/ipv6/configuration/guide/ip6-first_hop_security.html#wp1054246 Mick
