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Routing & Switching · Foundational

Passive Interface

An interface on which a routing protocol advertises the connected network but does not send hellos or form adjacencies.

Definition

Making user-facing interfaces passive prevents rogue adjacencies and reduces unnecessary protocol traffic while still advertising the subnet. In OSPF and EIGRP a passive interface sends no hellos at all. passive-interface default followed by no passive-interface on uplinks is a common hardening pattern.

Example

passive-interface GigabitEthernet0/2 under router ospf 1

Exam tip

For RIP, a passive interface still receives updates; for OSPF and EIGRP it neither sends nor processes hellos.

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