HP 6125G HP 6125G & 6125G/XG Blade Switches Layer 3 - IP Services Conf - Page 115

Address/prefix lease renewal

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Figure 50 Assignment involving four messages The assignment involving four messages operates in the following steps: 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 may 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 51, 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 51 Using the Renew message for address/prefix lease renewal As shown in Figure 52, 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. 107

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107
Figure 50
Assignment involving four messages
The assignment involving four messages operates in the following steps:
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 may 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 51
, 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 51
Using the Renew message for address/prefix lease renewal
As shown in
Figure 52
, 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.