first question : look at the sentence "ipv6 interfaces have link-local addresses in addition to the global addresses that applications usually use." a- link-local address is like a private address? b- what is the global address here ?(public (routable)) c- if a is a , b is b this is like NAT oh my god ? d- sentence i wrote above expresses that for one interface you can use more than one ip addresses ? second question a- link MTU ? (in fact i know it is the maximum sized packet that will go through a network) b- so what is path MTU ? third question : there is an auto configuration feature that comes with ipv6 also there are stateless and stateful ... stateful is dhcpv6 and stateless is a type of auto config ... auto config itself stateless auto config runs by sending a local-link multicast request to related router and gathering config parameters BUT DHCPv6 is like that(you send a request and get ip) , what is the difference?