-The special string 'dhcp' can be used for IP addresses to use DHCP, in which case no explicit gateway should be provided.
-For IPv6 the special string 'auto' can be used to use stateless autoconfiguration.
+The special string 'dhcp' can be used for IP addresses to use DHCP, in which case no explicit
+gateway should be provided.
+For IPv6 the special string 'auto' can be used to use stateless autoconfiguration. This requires
+cloud-init 19.4 or newer.