The specified time period is 40 seconds.
Interface subtype configuration mode
If you change the dead interval, the hello interval is automatically changed to a value that is one fourth that of the new dead interval, unless the hello interval is also explicitly configured using the ipv6 ospf hello-interval command.
The recommended setting is that:
The running-config command displays only explicitly configured values of the hello interval, which means that a value that was automatically changed as the result of a dead-interval change is not displayed.
The no form of the command restores the default value.
The following example sets the dead interval to 80 on a specific OSPFv3 Ethernet interface.
device# configure terminal device(config)# interface ethernet 1/1 device(conf-if-eth-1/1)# ipv6 ospf dead-interval 80