22.1.5 Information about the distribution prefix

The management information regarding assigned prefixes (hereafter lease information) is maintained by an IPv6 DHCP relay and used to configure routes. To check lease information, execute the show ipv6 dhcp relay binding operation command.

Note that distributed prefixes are managed by monitoring the PD option contained in IPv6 DHCP-PD. This means that distribution information is not monitored and routes are not automatically generated for packets to distribute IPv6 addresses because such packets do not include the PD option.

<Structure of this section>

(1) Trigger for changing lease information

The following table describes the events that prompt addition or deletion of lease information.

Table 22-2: Triggers when lease information is added or deleted
Description	Trigger
Addition	A distributed prefix is forwarded.
Deleted	Prefix release request forwarding*1
	A prefix lease has expired.
	Deleting the configuration set by the configuration command ipv6 dhcp relay destination that relays the prefix assignment#2
	Execute operation command copy <file> running-config *3
	Lease information is deleted by using the clear ipv6 dhcp relay binding operation command.

Note #1: Lease information is not deleted when the IPv6 DHCP relay receives a release request from an interface different from the one that received the distributed prefix. The release request itself is forwarded.
Note #2: The lease information regarding the prefix that is forwarded to the destination specified by using the ipv6 dhcp relay destination command is deleted.
Note #3: All lease information is deleted.

(2) Synchronizing Lease Information in a Stacked Configuration

In a stacked configuration, IPv6 DHCP relay keeps leased data on the master switch and on the backup switch, and synchronizes them all the time. If you change the lease information on the master switch, the master switch notifies the backup switch of the changes and synchronizes the information. Therefore, even if the master switch is switched, the new master switch can start operation using the lease information equivalent to the old master switch. However, if the master switch is switched during synchronization of lease information, only synchronized information can be carried over to the lease information.

(3) Transfer of information related to lease information

The following table describes whether the information related to lease information is passed. The related information that is created based on lease information is the information for automatically generating routes.

Table 22-3: Status of inheritance of lease information related information
Configuration	Operation of the equipment	Status of inheritance of related information (route auto-generated information)
Standalone	Restarting IPv6 DHCP Relay	OK^{#1 #2}
Standalone	When the Switch restarted	NG
Stack	Restarting IPv6 DHCP Relay	OK^{#1 #2}
	Switching the master switch	OK^{#1 #2 #3}
	Restart all member switches	NG

Legend: OK: Passing of information is guaranteed, NG: Information is deleted

Note #1

When you perform either of the following operations while the IPv6 DHCP relay program is being restarted, lease information might become invalid. If lease information becomes invalid, it will be deleted.

- The packet destination specified by using the ipv6 dhcp relay destination configuration command is deleted.

.Execute operation command copy <file> running-config (stand-alone mode)

Note #2

When the core-file parameter is specified in the restart ipv6-dhcp relay operation command, passing of information is not guaranteed.

Note #3

If the master switch is switched during synchronization of lease information in a stack configuration, the auto-generated route information is inherited only if the lease information is synchronized.