What command is used to configure all interfaces as OSPF passive interfaces by default?

The command used to configure all interfaces as OSPF passive interfaces by default is "passive-interface default." When you apply this command in OSPF configuration mode, it ensures that OSPF will not send or receive OSPF routing updates on any interfaces unless specified otherwise. This is particularly useful in situations where you want to enhance network security by preventing OSPF traffic from being sent over interfaces connected to networks where OSPF is not necessary.

By marking interfaces as passive, you can still participate in OSPF routing processes without exposing the router to potential security vulnerabilities related to OSPF messages. This command helps in maintaining efficient routing while reducing unnecessary OSPF traffic and helps ensure that OSPF updates are only sent over interfaces that require them.