Passive interface in OSPF
Suppose there was a router.
It has two interfaces.
Serial and Fas.
We set router ospf 1 to both of them.
However, the Fas does not need to send OSPF Hello from its interace.
This is because there are no such OSPF nodes.
We might set passive-interface to this in order to save router’s CPU.
Here is my question.
At this rate, Fas’s function is limited in receiving Hello.
This interface does not send Hello.
It means the neighbor OSPF relation would be collapsed.
OSPF would not work in here.
Then, what is the meaning of setting passive-interface?
We do not have to set any OSPF related command in the Fas from the scratch.