In what condition does silent-interface need to be configured to make a port become a passive-interface?
To advertise a direct route on a router, use the import direct command to redistribute the direct route. However, the resulted External LSAs are advertised to the whole autonomous system domain (except the stub area), causing widespread influences. To restrict the range of direct route advertisement, use the network command to enable OSPF on the interface. Use the silent-interface command to make the port become a passive-interface. This prevents the interface from sending Hello packets from the interface to establish a neighbor relationship. In this way, the direct route is advertised as an intra-area route. On one hand, this greatly reduces the size of the routing table of the OSPF routing domain; on the other hand, this reduces the CPU occupation of the router by preventing the system from sending the Hello packets between interfaces to establish neighbor relationships.