Previously, facter did not fully provide facts for IPv6 addresses. As a result, the netmask6 and netmaks6_<interface> facts were missing.
With this update, the 'netmask6' family of facts are added to Facter 2.x. This updates lib/facter/util/ip.rb, lib/facter/util/netmask.rb, and lib/facter/interfaces.rb files. As a result, facter returns netmask for default IPv6 address and IPv6 interfaces with an IPv6 address.