IPv6 Implications for TCP/UDP Port Scanning

The 128 bits of IPv6 address space is considerably bigger than the 32 bits of address space in IPv4. In particular, the IPv6 subnets to which hosts attach will by default have 64 bits of host address space. As a result, traditional methods of remote TCP or UDP port scanning to discover open or running services on a host will potentially become far less computationally feasible, due to the larger search space in the subnet. This document discusses that property of IPv6 subnets, and describes related issues for site administrators of IPv6 networks to consider, which may be of importance when planning site address allocation and management strategies.