H3C Technologies H3C S12500 Series Switches - Manual (Page 143)

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Figure 49 Assignment involving four messages
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Address/prefix lease renewal
An IPv6 address/prefix assigned by a DHCPv6 server has a valid lifetime. After the valid lifetime expires,
the DHCPv6 client cannot use the IPv6 address/prefix. To use the IPv6 address/prefix, the DHCPv6 client
must renew the lease time.
Figure 50 Using the Renew message for address/prefix lease renewal
As shown in
782H
Figure 50 , at T1, the DHCPv6 client sends a Renew message to the DHCPv6 server. The
recommended value of T1 is half the preferred lifetime. The DHCPv6 server responds with a Reply
message, informing the client about whether or not the lease is renewed.
Figure 51 Using the Rebind message for address/prefix lease renewal
As shown in
783H
Figure 51 , if the DHCPv6 client receives no response from the DHCPv6 server after sending
a Renew message at T1, it multicasts a Rebind message to all DHCPv6 servers at T2 (when 80% preferred
lifetime elapses). 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 any DHCPv6 server before the valid lifetime expires, the
client stops using the address/prefix.
For more information about the valid lifetime and the preferred lifetime, see "Configuring IPv6 basics."