DHCPv6 lease times on a Cisco IOS device

When configuring a DHCPv6 server on a Cisco IOS device, you can specify the lease time using the following command under the IPv6 DHCP configuration mode:

R1(config)#ipv6 dhcp pool my_pool R1(config-dhcpv6)#information refresh ? <0-365> Days infinite Infinite lease

The lease time interval is represented by a 32 bit value, and is measured in seconds. On a Cisco device, it is configured in days, as seen above.

A lease time value of all ones in the 32-bit value indicates an infinite lease time. This corresponds to a decimal value of 4294967295.

By default, the lease time for a DHCPv6 server on a Cisco IOS device is 30 days.

To view the configured lease time, issue the following command

R1(config)#exit R1#show ipv6 dhcp pool DHCPv6 pool: my_pool Information refresh: 4294967295 Active clients: 0 R1#

Notice the above information shows a value of 4294967295 seconds which indicates an infinite lease time.

https://datatracker.ietf.org/doc/html/rfc8415#page-127