The default value is 10 seconds.
Interface subtype configuration mode
If you change the hello interval, the dead interval is automatically changed to a value that is four times that of the new hello interval, unless the dead interval is also explicitly configured using the ip ospf dead-interval command.
The recommended setting is that:
The running-config command displays only explicitly configured values of the dead interval, which means that a value that was automatically changed as the result of a hello-interval change is not displayed.
The no form of the command restores the default value.
The following example sets the hello interval to 50 on a specific OSPFv2 virtual Ethernet (VE) interface:
device# configure terminal device(config)# interface ve 1 device(config-if-Ve-1)# ip ospf hello-interval 50