Address/prefix lease renewal
The IPv6 address/prefix assigned by the DHCPv6 server has a lease time, which depends on the valid lifetime. When the valid lifetime of the IPv6 address/prefix expires, the DHCPv6 client cannot use the IPv6 address/prefix any longer. To continue using the IPv6 address/prefix, the DHCPv6 client has to renew the lease time.
As shown in Figure 62, at T1, the DHCPv6 client unicasts a Renew message to the DHCPv6 server that assigned the IPv6 address/prefix to the DHCPv6 client. The recommended value of T1 is half the preferred lifetime. Then the DHCPv6 server responds with a Reply message, informing the client about whether or not the lease is renewed.
Figure 62: Using the Renew message for address/prefix lease renewal
As shown in Figure 63, if the DHCPv6 client receives no response from the DHCPv6 server after sending out a Renew message at T1, it multicasts a Rebind message to all DHCPv6 servers at T2 (that is, when 80% preferred lifetime expires). Then the DHCPv6 server responds with a Reply message, informing the client about whether or not the lease is renewed.
If the DHCPv6 client receives no response from the DHCPv6 servers, the client stops using the address/prefix when the valid lifetime expires. For more information about the valid lifetime and the preferred lifetime, see "Configuring IPv6 basics."
Figure 63: Using the Rebind message for address/prefix lease renewal
