Porting discovery assumptions that worked for IPv4 to the IPv6 network produces incomplete results. Neighbor discovery and the size of the address space require a different approach.
Basic approach
IPv6 Neighbor Discovery uses ICMPv6 messages to learn about neighbors and routers on the same link. It is impractical to try all addresses in a standard /64 subnet sequentially. Known addresses, operating system neighbor registers, and managed inventory are more meaningful starting sources.
Application steps
- Examine the operating system's IPv6 neighbor and route tables read-only.
- Compare DNS AAAA records with addresses in the managed device list.
- Evaluate with the network administrator the rules implemented for ICMPv6 on the firewall; Don't block all messages indiscriminately.
Practical example
A printer may appear in the IPv4 discovery but not in the IPv6 list. This may be because the device is only discovered via known addresses or because IPv6 services are configured differently; No two lists should be expected to be equal.
Interpret the result correctly
This guide describes IPv6 discovery methods; It does not mean that a particular scanner supports all methods. Clearly stating the protocol used and address scope in the resulting report prevents misinterpretation of the omission as device loss.
Source and follow-up reading
Protocol or command details: RFC 4861. The steps and example scenario are IPScans editorial narrative.