Information about passive routes is put in NCP’s and NCPROUTE’s routing tables. A passive entry in NCPROUTE’s routing table is used as a placeholder to prevent a route from being propagated and from being overwritten by a competing RIP route. With the exception of directly-connected passive routes, passive routes are not propagated; they are known only by this router.
Using passive routes can create routing loops, so care must be taken when creating them.
Passive routes should be used when adding routes where the host or network is not running RIP. Passive routes should also be used when adding a default route, because this is the only way to prevent a route from timing out.