HP VPN Firewall Appliances Network Management Configuration Guide

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The assignment involving four messages operates as follows:
1. The DHCPv6 client sends out a Solicit message, requesting an IPv6 address/prefix and other
configuration parameters.
2. If the Solicit message does not contain a Rapid Commit option, or if the DHCPv6 server does not
support rapid assignment even though the Solicit message contains a Rapid Commit option, the
DHCPv6 server responds with an Advertise message, informing the DHCPv6 client of the
assignable address/prefix and other configuration parameters.
3. The DHCPv6 client might receive multiple Advertise messages offered by different DHCPv6 servers.
It then selects an offer according to the receiving sequence and server priority, and sends a
Request message to the selected server for the confirmation of assignment.
4. The DHCPv6 server sends a Reply message to the client, confirming that the address/prefix and
other configuration parameters are assigned to the client.
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 368, at
T1, the DHCPv6 client send
s a Renew message to the DHCPv6 server. 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 368 Using the Renew message for address/prefix lease renewal
As shown in Figure 369, 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.
Figure 369 Using the Rebind message for address/prefix lease renewal