By default, OSPF Helper mode is enabled when OSPF is configured. You can disable helper mode by the following command and re-enable it again by using no or default operators.
enable
configure terminal
router ospf
helper-mode-disable
no helper-mode-disable
Or
default helper-mode disable
Disable Helper mode:
Switch:1>enable Switch:1#configure terminal Switch:1(config)#router ospf Switch:1(config-ospf)#helper-mode-disable
Enable Helper mode:
Switch:1>enable Switch:1#configure terminal Switch:1(config)#router ospf Switch:1(config-ospf)#no helper-mode-disable