Cisco DHCPv6 Server Configuration

DHCPV6(config)#ipv6 dhcp pool STATEFUL
DHCPV6(config-dhcpv6)#address prefix 2001:1111:1111:1111::/64
DHCPV6(config-dhcpv6)#dns-server 2001:4860:4860::8888
DHCPV6(config-dhcpv6)#domain-name NETWORKLESSONS.LOCAL
DHCPV6(config)#interface FastEthernet 0/0
DHCPV6(config-if)#ipv6 address 2001:1111:1111:1111::1/64
DHCPV6(config-if)#ipv6 dhcp server STATEFUL
DHCPV6(config-if)#ipv6 nd managed-config-flag
DHCPV6(config-if)#ipv6 nd prefix 2001:1111:1111:1111::/64 14400 14400 no-autoconfig

Totally lost here. The above is taken from the DHCPv6 Server config lesson. It’s regarding configuration of a Stateful DHCPv6 server.

  1. Don’t global unicast prefixes need to come from an ISP to ensure they are unique? If so, why would there be a need to manually configure one anywhere? Shouldn’t a router already have this prefix from the ISP?
  2. What happens if you accidentally type in the wrong global unicast prefix and it doesn’t match what the ISP assigned you? Couldn’t this risk address collision?
  3. Assuming you are getting the prefix from the ISP, why are you manually assigning an IPv6 address to this interface? Can’t it just get one as a DHCPv6 client or use SLAAC from the ISP-provided prefix?
  4. Why are you manually typing in the 2001:1111:1111:111::/64 prefix in the ipv6 nd prefix command? You already assigned an address to the interface. Couldn’t you just use the default parameter? Cisco NetAcad does this.
  5. What’s with the 4-hour lifespans on that prefix? What would happen when those 14,400 seconds expire?

Sorry for all the questions. This topic has me completely stumped.