I'm studying networking and GNS3. In every example I see that before configuring an IP (IPv4 or IPv6) address of an interface, there is always the command "no ip address". Why they write this command? I mean, when I set a new IP the old IP will be lost so I don't understand the reason of writing "no ip address". I also do not understand why sometimes before an IPv6 address there is "no ip address" and other times there is "no ipv6 address" (same device, same function, just different examples). Can someone explain it?