The passive interface feature is used to make a routing protocol accept routing information from neighbors, but prevent information from being advertised to neighbors.
However, when this feature is used with Enhanced Interior Gateway Routing Protocol (EIGRP), it prevents the router from learning and advertising routes.
EIGRP discovers neighbors using hello messages before accepting routes and installing them in the routing table. Hello messages are normally sent and received on an interface configured for EIGRP.
However, the passive interface feature in EIGRP makes an interface stop sending and receiving hello messages. This tears down any existing neighbor relationships and stops learning routes from any EIGRP neighbors available on the interface and configured as passive.
To configure an interface as passive in EIGRP, issue the passive-interfaceinterface-type interface-number command in router configuration mode for EIGRP.
To make EIGRP learn routes from a neighbor connected to an interface, but prevent advertising routes to the neighbor, use the route-filtering techniques instead of the passive interface feature.