209PDThe DHCPv6 server creates a prefix delegation (PD) for each assigned prefix to record the IPv6 prefix,client DUID, IAID, valid lifetime, preferred lifetime, lease expiration time, and IPv6 address of therequesting client.DHCPv6 address poolThe DHCP server selects IPv6 addresses, IPv6 prefixes, and other parameters from an address pool, andassigns them to the DHCP clients.Address allocation mechanismsDHCPv6 supports the following address allocation mechanisms:• Static address allocation—To implement static address allocation for a client, create a DHCPv6address pool, and manually bind the DUID and IAID of the client to an IPv6 address in the DHCPv6address pool. When the client requests an IPv6 address, the DHCPv6 server assigns the IPv6address in the static binding to the client.• Dynamic address allocation—To implement dynamic address allocation for clients, create aDHCPv6 address pool, specify a subnet for the pool, and divide the subnet into temporary andnon-temporary IPv6 address ranges. Upon receiving a DHCP request, the DHCPv6 server selects anIPv6 address from the temporary or non-temporary IPv6 address range based on the address typein the client request.Prefix allocation mechanismsDHCPv6 supports the following prefix allocation mechanisms:• Static prefix allocation—To implement static prefix allocation for a client, create a DHCPv6 addresspool, and manually bind the DUID and IAID of the client to an IPv6 prefix in the DHCPv6 addresspool. When the client requests an IPv6 prefix, the DHCPv6 server assigns the IPv6 prefix in the staticbinding to the client.• Dynamic prefix allocation—To implement dynamic prefix allocation for clients, create a DHCPv6address pool and a prefix pool, specify a subnet for the address pool, and apply the prefix pool tothe address pool. Upon receiving a DHCP request, the DHCPv6 server dynamically selects an IPv6prefix from the prefix pool in the address pool.Address pool selectionThe DHCPv6 server observes the following principles to select an IPv6 address or prefix for a client:1. If there is an address pool where an IPv6 address is statically bound to the DUID or IAID of theclient, the DHCPv6 server selects this address pool and assigns the statically bound IPv6 addressor prefix and other configuration parameters to the client.2. If the receiving interface has an address pool, the DHCP server selects an IPv6 address or prefixand other configuration parameters from this address pool.3. If there is no static address pool and the receiving interface has no address pool, the DHCPv6server selects an address pool in the following way:{ If the client and the server reside on the same subnet, the DHCP server matches the IPv6 addressof the receiving interface against the subnets of all address pools, and selects the address poolwith the longest-matching subnet.{ If the client and the server reside on different subnets (a DHCPv6 relay agent is in-between), theDHCPv6 server matches the IPv6 address of the DHCPv6 relay agent interface closest to the
