Passive Interfaces

We can tell OSPF to advertise the network on an interface without sending OSPF packets out through that interface. This is appropriate when there is no other router on the subnet. The concept of a passive interface also exists in other routing protocols. The way we configure this does vary from manufacturer to manufacturer. On many vendor’s equipment, you explicitly add an OSPF interface to a physical or virtual interface. With Cisco equipment, we define the networks we will advertise and then make the interface passive if we do not want to egress routing packets.In OSPF a passive interface also makes an interface a stub network, this is significant, see below.